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  • Other Sources  (278)
  • SOLAR PHYSICS  (278)
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  • 1987  (278)
  • 1
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    Active region influences upon the solar constant (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The influence that active regions have upon the solar constant is discussed. Sunspots appear to lower the solar constant for the few days in which they are located near central meridian. This raises the possibility that an 11-year, solar-cycle-related depression in the solar constant may occur. Recent findings concerning the physics of active regions suggest that sunspots and faculae are largely surface features. Within that surface faculae reradiate, within a few weeks, the 'missing energy' associated with sunspots. This is consistent with the observations showing that the solar constant does not have an 11-year cycle-related depression that some authors predicted. However, there is a secular variation in the solar constant, whose explanation is not completely understood.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 818-822
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  • 2
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    Flare research with the NASA/MSFC vector magnetograph - Observed characteristics of sheared magnetic fields that produce flares (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The present MSFC Vector Magnetograph has sufficient spatial resolution (2.7 arcsec pixels) and sensitivity to the transverse field (the noise level is about 100 gauss) to map the transverse field in active regions accurately enough to reveal key aspects of the sheared magnetic fields commonly found at flare sites. From the measured shear angle along the polarity inversion line in sites that flared and in other shear sites that didn't flare, evidence is found that a sufficient condition for a flare to occur in 1000 gauss fields in and near sunspots is that both: (1) the maximum shear angle exceed 85 degrees; and (2) the extent of strong shear (shear angle of greater than 80 degrees) exceed 10,000 km.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 113; 1-2,; 347-352
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  • 3
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    Nonlocal thermal transport in solar flares (1987)
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    Publication Date: 2011-08-19
    Description: A flaring solar atmosphere is modeled assuming classical thermal transport, locally limited thermal transport, and nonlocal thermal transport. The classical, local, and nonlocal expressions for the heat flux yield significantly different temperature, density, and velocity profiles throughout the rise phase of the flare. Evaporation of chromospheric material begins earlier in the nonlocal case than in the classical or local calculations, but reaches much lower upward velocities. Much higher coronal temperatures are achieved in the nonlocal calculations owing to the combined effects of delocalization and flux limiting. The peak velocity and momentum are roughly the same in all three cases. A more impulsive energy release influences the evolution of the nonlocal model more than the classical and locally limited cases.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 320; 904-912
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  • 4
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    Explorations of electric current system in solar active regions. I - Empirical inferences of the current flows (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Techniques to identify sources of electric current systems and their channels of flow in solar active regions are explored. Measured photospheric vector magnetic fields together with high-resolution white-light and H-alpha filtergrams provide the data base to derive the current systems in the photosphere and chromosphere. As an example, the techniques are then applied to infer current systems in AR 2372 in early April 1980.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 109; 2, 19; 307-320
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  • 5
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    Comparisons of interplanetary type III storm footpoints with solar features (1987)
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    Publication Date: 2011-08-19
    Description: The trajectories of 38 type III storms in the interplanetary medium have been deduced from ISEE-3 radio observations and extrapolated back to the sun to determine the Carrington coordinates of their footpoints. The analysis assumes radial motion of the solar wind, and the trajectories are projected radially back toward the surface for the last few solar radii. To identify the storm sources, the footpoints were compared to a variety of solar features: to the large-scale neutral line at the base of the current sheet, to active regions, to the small-scale neutral lines and H-alpha filaments which trace out active regions, and to coronal holes. Most of the footpoints were found to lie near active regions, in agreement with metric storm locations. There is a weak correlation with H-alpha filaments, no apparent association with the current sheet, and an anticorrelation with coronal holes. There is a small excess of storms in the leading half of magnetic sectors.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 109; 1, 19
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  • 6
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    Multiperiodic irradiance changes caused by r-modes and g-modes (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: More than 20 real periodicities ranging from 20 days to 2 years modulate the solar irradiance data accumulated since November 1978 by Nimbus 7. Many are quite strong during the first three years (solar maximum) and weak after that. There is a high correspondence between periods in irradiance and 28 periods predicted from the rotation and beating of global solar oscillations (r-modes and g-modes). Angular states l = 1, 2, and 3 are detected as well as some unresolved r-mode power at higher l. The prominence of beat periods implies a nonlinear system whose effective nonlinear power was measured to be about 2. This analysis constitutes a detection of r-modes in the sun, and determines from them a mean sidereal rotation rate for the convective envelope of 459 + or - 4 nHz which converts to a period of 25.2 days (27.1d, synodic).
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 109; 1, 19
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  • 7
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    Meridional transport of magnetic flux in the solar wind between 1 and 10 AU - A theoretical analysis (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations suggesting that the mean solar wind azimuthal field strength B(theta) near the ecliptic plane falls off more rapidly with heliocentric distance than would be expected in a classic Parker expansion is reexamined from a theoretical perspective using a three-dimensional MHD nonlinear numerical model for steady, corotating flow. For realistic solar wind parameters, it is found that a purely axisymmetric expansion can produce sizable magnetic flux deficits only when there are substantial meridional gradients in mean flow conditions localized about the ecliptic plane near the sun. Calculations on three-dimensional cororating flows are presented which demonstrate that latitudinal transport of magnetic flux by stream interactions may be an important consideration in generating the deficits in mean B(theta).
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 7241-725
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  • 8
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    The thermal stability of coronal loops by nonlinear diffusion asymptotics (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A nonlinear reaction-diffusion equation and some additional constraints are derived which describe the time-dependent behavior of the temperature structure of the plasma in coronal loops. The equation is analyzed using nonlinear diffusion asymptotics, in particular singular perturbation techniques, and the results are interpreted in the context of the physical problem of the thermal stability and temporal behavior of the plasma. The results are consistent with the possibility of cyclic thermal behavior of the plasma, as suggested by Kuin and Martens (1982).
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 179; 1-2,
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  • 9
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    Nonlinear radiative condensation in a sheared magnetic field (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A well-resolved two-dimensional nonlinear numerical simulation of the radiative/thermal instability in a sheared magnetic field is described which leads to filament formation. The condensation is initiated by a linearly unstable mode and widens until it is slowed by thermal conduction parallel to B. During the nonlinear evolution, the minimum temperature falls from 10 to the 6th K to 10 to the 4th K and eventually reaches a state of local thermal equilibrium in about five e-folding times.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 317; L91-L94
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  • 10
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    Nuclear processes and accelerated particles in solar flares (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Nuclear processes and particle acceleration in solar flares are reviewed. The theory of gamma-ray and neutron production is discussed and results of calculations are compared to gamma-ray, neutron, and charged-particle observations from solar flares. The implications of these comparisons on particle energy spectra, total numbers, anisotropies, electron-to-proton ratios, as well as on acceleration mechanisms and the interaction site, are presented. The information on elemental and isotopic abundances derived from gamma-ray observations is compared to abundances obtained from escaping accelerated particles and other sources.
    Keywords: SOLAR PHYSICS
    Type: Space Science Reviews (ISSN 0038-6308); 45; 3-4,
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  • 11
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    On the prospect of using butterfly diagrams to predict cycle minimum (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Features enabling the prediction of the beginning and the length of a solar cycle, in addition to the turning points in the period-growth dichotomy, have been identified based on butterfly diagrams for the period from 1874 to the present. The present results indicate that cycle 21 will be a long-period cycle ending after July 1987. On the assumption that April 1985 was the first occurrence of high latitude new cycle (cycle 22) spots during the decline of cycle 21 (the old cycle), it is suggested that the last occurrence of high latitude old cycle spots was September 1983 and that the minimum for cycle 22 will be about 1986.7 + or - 1.1 yr.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 111; 2, 19; 255-265
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  • 12
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    10.7-cm solar radio flux and the magnetic complexity of active regions (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: During sunspot cycles 20 and 21, the maximum in smoothed 10.7-cm solar radio flux occurred about 1.5 yr after the maximum smoothed sunspot number, whereas during cycles 18 and 19 no lag was observed. Thus, although 10.7-cm radio flux and Zurich sunspot number are highly correlated, they are not interchangeable, especially near solar maximum. The 10.7-cm flux more closely follows the number of sunspots visible on the solar disk, while the Zurich sunspot number more closely follows the number of sunspot groups. The number of sunspots in an active region is one measure of the complexity of the magnetic structure of the region, and the coincidence in the maxima of radio flux and number of sunspots apparently reflects higher radio emission from active regions of greater magnetic complexity. The presence of a lag between sunspot-number maximum and radio-flux maximum in some cycles but not in others argues that some aspect of the average magnetic complexity near solar maximum must vary from cycle to cycle. A speculative possibility is that the radio-flux lag discriminates between long-period and short-period cycles, being another indicator that the solar cycle switches between long-period and short-period modes.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 111; 2, 19; 279-285
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  • 13
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    On the proposed associations of solar neutrino flux with solar particles, cosmic rays, and the solar activity cycle (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 112; 1, 19; 1-15
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  • 14
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    Microwave emission above steady and moving sunspots (1987)
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    Publication Date: 2011-08-19
    Description: Two-dimensional maps of radio brightness temperature and polarization, computed assuming thermal emission with free-free and gyroresonance absorption, are compared with observations of active region 2502, performed at Westerbork at lambda = 6.16 cm during a period of 3 days in June 1980. The computation is done assuming a homogeneous model in the whole field of view and a force-free extrapolation of the photospheric magnetic field observed at MSFC with a resolution of 2.34 arcsec. The mean results are the following: (1) a very good agreement is found above the large leading sunspot of the group, assuming a potential extrapolation of the magnetic field and a constant conductive flux in the transition region ranging from .2 x 10 to the 6th to 10 to the 7th erg/sq cm 5; (2) a strong radio source, associated with a new-born moving sunspot, cannot be ascribed to thermal emission. It is suggested that this source may be due to synchrotron radiation by mildly relativistic electrons accelerated by resistive instabilities occurring in the evolving magnetic configuration. An order-of-magnitude computation of the expected number of accelerated particles seems to confirm this hypothesis.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 112; 1, 19
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  • 15
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    Radio range measurements of coronal electron densities at 13 and 3.6 centimeter wavelengths during the 1985 solar conjunction of Voyager 2 (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 323; L141-L14
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  • 16
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    Transient ionization and solar flare X-ray spectra (1987)
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    Publication Date: 2011-08-19
    Description: In this paper the effects of a transiently ionizing solar flare plasma on the X-ray spectrum of iron between 1.85 and 1.92 A are considered. The atomic physics of the nonequilibrium spectrum is discussed, and reasons for differences in appearance from ionization equilibrium spectra are explained. The effect of spectral resolution on the ability to detect transient ionization in the iron X-ray spectrum is illustrated by synthetic spectra. A synthetic transiently ionizing spectrum is applied to the interpretation of spectra obtained from the SOX 1 spectrometer on the Japanese Hinotori spacecraft. Some indications of transient ionization are found, although counting statistics negate a strong conclusion. A hypothetical spectrometer with about one order of magnitude more sensitivity than the SOX 1 Hinotori or the bent crystal spectrometer flown on the Solar Maximum Mission (SMM) is also considered. The ranges of plasma parameters such as plasma emission measure and density that are necessary for transient ionization to be detected by such an instrument are discussed.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 323; 799-809
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  • 17
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    Microflares in the solar magnetic network (1987)
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    Publication Date: 2011-08-19
    Description: Localized brightenings are found throughout the magnetic network in quiet sun image sequences obtained in the C IV 1548 A line by the SMM satellite's UV spectrometer and polarimeter. Some bright sites are short-lived, while others persist. Plots of the intensity fluctuations show that the enhancements at both short- and long-lived sites are the result of localized impulsive heating events that occur intermittently at the short-lived sites and in more rapid succession at the long-lived ones. The number of these events and their visibility in the wings of the C IV line are consistent with their identification as the explosive events seen in UV spectra.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 323; 380-390
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  • 18
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    The detection of global convection on the sun by an analysis of line shift data of the John M. Wilcox Solar Observatory at Stanford University (1987)
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    Publication Date: 2011-08-19
    Description: An analysis of the absorption line shift data of the John M. Wilcox Solar Observatory at Stanford University has yielded signatures of the existence of global convection on the sun. These include persistent periodic time variations in the east-west component of the velocity fields defined by fitting a slope to the line shift data in a certain longitude window at a specified latitude and longitude by the least squares method. The amplitude of the velocity fields estimated from these variations is of the order of 100 m/s. The results of the analysis also suggest that several modes of global convection coexist in the solar convection zone. Details of the analysis are given.
    Keywords: SOLAR PHYSICS
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  • 19
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    Hard X-ray and radio emission at the onset of great solar flares (1987)
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    Publication Date: 2011-08-19
    Description: A study of the onset phase of ten great hard X-ray bursts is presented. It is shown from hard X-ray and radio observations in different wavelength ranges that the energization of the electrons proceeds on a global time-scale for some tens of seconds. In nine of the bursts, two phases of emission can be distinguished during the onset phase: the preflash phase (during which emission up to an energy limit ranging from some tens of keV to 200 keV is observed) followed ten to some tens of seconds later by the flash phase (where the count rate in all detector channels rises simultaneously to within some seconds). For two of the events, strong gamma-ray line emission is observed and is shown to start close to the onset of the flash phase.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 111; 1, 19
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  • 20
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    Varying self-inductance and energy storage in a sheared force-free arcade (1987)
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    Publication Date: 2011-08-19
    Description: An electric circuit analogy is used to model the build-up and storage of magnetic energy in the coronal loops known to exist in the atmosphere of the sun. The present parameterization of magnetic energy storage in an electric circuit analog uses a bulk current I flowing in the circuit and a self-inductance L. Because the self-inductance is determined by the geometry of the magnetic configuration any change in its dimensions will change L. If L is increased, the amount of magnetic energy stored and the rate at which magnetic energy is stored are both increased. One way of increasing L is to shear the magnetic field lines and increase their effective geometrical length. Using the force-free field approximation for a magnetic arcade whose field lines are sheared by photospheric motions, it is demonstrated that the increase of magnetic energy is initially due to the increase of the current intensity I and later mainly due to the increase of the self-inductance.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 180; 1-2,; 218-222
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  • 21
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    Spherical harmonic analysis of steady photospheric flows (1987)
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    Publication Date: 2011-08-19
    Description: A technique is presented in which full disk Doppler velocity measurements are analyzed using spherical harmonic functions to determine the characteristics of the spectrum of spherical harmonic modes and the nature of steady photospheric flows. Synthetic data are constructed in order to test the technique. In spite of the mode mixing due to the lack of information about the motions on the backside of the sun, solar rotation and differential rotation can be accurately measured and monitored for secular changes, and meridional circulations with small amplitudes can be measured. Furthermore, limb shift measurements can be accurately obtained, and supergranules can be fully resolved and separated from giant cells by their spatial characteristics.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 108; 1, 19
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  • 22
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    Heating of the solar corona by the resonant absorption of Alfven waves (1987)
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    Publication Date: 2011-08-19
    Description: An improved method for calculating the resonance absorption heating rate is discussed and the results are compared with observations in the solar corona. To accomplish this, the wave equation for a dissipative, compressible plasma is derived from the linearized magnetohydrodynamic equations for a plasma with transverse Alfven speed gradients. For parameters representative of the solar corona, it is found that a two-scale description of the wave motion is appropriate. The large-scale motion, which can be approximated as nearly ideal, has a scale which is on the order of the width of the loop. The small-scale wave, however, has a transverse scale much smaller than the width of the loop, with a width of about 0.3-250 km, and is highly dissipative. These two wave motions are coupled in a narrow resonance region in the loop where the global wave frequency equals the local Alfven wave frequency. Formally, this coupling comes about from using the method of matched asymptotic expansions to match the inner and outer (small and large scale) solutions. The resultant heating rate can be calculated from either of these solutions. A formula derived using the outer (ideal) solution is presented, and shown to be consistent with observations of heating and line broadening in the solar corona.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 317; 514-521
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  • 23
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    On the apparent velocity of integrated sunlight. I - 1983-1985 (1987)
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    Publication Date: 2011-08-19
    Description: Frequency measurements for the Delta V = 2 transitions of CO in the integrated light spectrum of the sun are presented. The nature and magnitude of systematic errors which typically arise in absolute velocity measurements of integrated sunlight are explored in some detail, and measurements believed accurate at the level of about 5 m/s or less are presented. It is found that the integrated light velocity varies by about 3 m/s or less over a one-day period. Over the long term, the data indicate an increasing blue-shift in these weak infrared lines amounting to 30 m/s from 1983 to 1985. The sense of the drift is consistent with a lessening in the magnetic inhibition of granular convection at solar minimum. Such an effect has implications for the spectroscopic detectability of planetary-mass companions to solar-type stars.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 316; 771-787
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  • 24
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    Changes in measured vector magnetic fields when transformed into heliographic coordinates (1987)
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    Publication Date: 2011-08-19
    Description: The changes that occur in measured magnetic fields when they are transformed into a heliographic coordinate system are investigated. To carry out this investigation, measurements of the vector magnetic field of an active region that was observed at 1/3 the solar radius from disk center are taken, and the observed field is transformed into heliographic coordinates. Differences in the calculated potential field that occur when the heliographic normal component of the field is used as the boundary condition rather than the observed line-of-sight component are also examined. The results of this analysis show: (1) that the observed fields of sunspots more closely resemble the generally accepted picture of the distribution of umbral fields if they are displayed in heliographic coordinates; (2) that the differences in the potential calculations are less than 200 G in field strength and 20 deg in field azimuth outside sunspots; and (3) that differences in the two potential calculations in the sunspot areas are no more than 400 G in field strength but range from 60 to 80 deg in field azimuth in localized umbral areas.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 107; 2, 19; 239-246
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  • 25
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    Nonlinear evolution of radiation-driven thermally unstable fluids (1987)
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    Publication Date: 2011-08-19
    Description: The nonlinear evolution of a radiation-driven thermally unstable planar fluid is simulated numerically using a semiimplicit finite-difference algorithm. When the equilibrium state of the fluid is perturbed by random initial excitation of the velocity field, dense, cool, two-dimensional structures are found to form in a rarer, warmer surrounding medium. The nonlinear phase of evolution is characterized by the turbulent contraction of the condensed region, accompanied by a significant increase in the amount of energy radiated. It is found that, if the random velocity perturbation has a sufficiently large amplitude, the fluid will not form condensed structures. Finally, the relationship of these results to observations of the solar chromosphere, transition region, and corona is discussed.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 315; 385-407
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  • 26
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    Solar irradiance change and special longitudes due to r-modes (1987)
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    Publication Date: 2011-08-19
    Description: Sluggish global oscillations, having a periodicity of months and trapped in the sun's convection zone, modulate the amount of energy reaching earth and seem to impose some large-scale order on the distribution of solar surface features. These recently recognized oscillations (r-modes) increase the predictability of solar changes and may improve understanding of rotation and variability in other stars. Most of the 13 periodicities ranging from 13 to 85 days that are caused by r-modes can be detected in Nimbus 7 observations of solar irradiance during 3 years at solar maximum. These modes may also bear on the classical question of persistent longitudes of high solar activity.
    Keywords: SOLAR PHYSICS
    Type: Science (ISSN 0036-8075); 235; 1631-163
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  • 27
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    Nonpotential features observed in the magnetic field of an active region (1987)
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    Publication Date: 2011-08-19
    Description: A unique coordinated data set consisting of vector magnetograms, H-alpha photographs, and high-resolution ultraviolet images of a solar active region is used, together with mathematical models, to calculate potential and force-free magnetic field lines and to examine the nonpotential nature of the active region structure. It is found that the overall bipolar magnetic field of the active region had a net twist corresponding to net current of order 3 x 10 to the 12th A and average density of order 4 x 10 to the -4th A/sq m flowing antiparallel to the field. There were three regions of enhanced nonpotentiality in the interior of the active region; in one the field had a marked nonpotential twist or shear with height above the photosphere. The measured total nonpotential magnetic energy stored in the entire active region was of order 10 to the 32nd ergs, about 3 sigma above the noise level.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 314; 782-794
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  • 28
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    Solar wind stream structure at large heliocentric distances Pioneer observations (1987)
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    Publication Date: 2011-08-19
    Description: Time profiles and histograms of plasma data from Pioneers 10 and 11 are examined for the period between 1975 and 1983. During this time, Pioneer 10 traveled between a heliocentric distance of 8.7 and 30.4 AU. The velocity structure of the solar wind at these heliocentric distances is found to have one of two distinct forms: approximately 70 percent of the time the solar wind has a nearly flat velocity profile. Occasionally, this flat velocity profile is accompanied by quasi-periodic variations in density and in thermal speed consistent with the concept that the 'corotating interaction regions' which are produced by the interaction of high- and low-speed streams at intermediate heliocentric distances are replaced by 'pressure regions' in the outer heliosphere. The remaining 30 percent of the time the solar wind is marked by large (50-200 km/s) long-term (30-120 days) shifts in the average solar wind velocity.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 2231-224
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    Predictions for the total solar eclipse of 1988 (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A total eclipse of the sun will be widely visible from the East Indies on March 18, 1988. Detailed predictions for this event are presented which include tables of geographic coordinates for the northern limit, center line and southern limit of the path of totality, local circumstances for 40 cities within the total and partial eclipse paths, the lunar-limb profile, and maps depicting the path of totality. The author discusses the general characteristics of the eclipse, local circumstances from various points along the central path and the Saros-series history.
    Keywords: SOLAR PHYSICS
    Type: Royal Astronomical Society of Canada, Journal (ISSN 0035-872X); 81; 44-60
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    Preflare energy build-up in a filament circuit (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The May 16, 1981 flare observed at Debrecen is studied by extending to a fully three-dimensional model the two-dimensional Van Tend and Kuperus (1978) scenario for preflare energy build-up. It is shown that there are 10 to the 33rd ergs of free energy available to explain the subsequent large two-ribbon flare. As a result of the three-dimensional character of the present model, this estimate is an order of magnitude larger than that made by Van Tend. It is confirmed that the global form of the preflare circuit is highly important in determining the amount of energy stored in the preflare configuration. The present model gives correct predictions for the independently observed photospheric flow velocity and current strength in filaments.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 107; 1, 19; 95-108
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  • 31
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    Large-scale fluctuations in the interplanetary medium (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Power spectra of measurements of the magnetic field strength in the heliosphere obtained by Voyager 1 between 1 AU and 9 AU have the form of a power law f exp -a from periods of several hours to at least 6 days. The exponent was a = 2.0 + or - 0.05 for all of the spectra considered, which is the exponent for a series of steps and for Burgers' (1971) turbulence. Spectra of large-scale speed fluctuations also have the form f exp - b from a period of a few hours to periods greater than 13 days in the region from 1 AU to 8.9 AU. The exponent b is generally somewhat larger than b = 2, implying some 'persistence' of the speed fluctuations. The low-frequency cutoff (outer cutoff) of the power law increases from a period of 6.5 days at 1 AU to 26 days at (6.1-8.9) AU, which can be attributed to: (1) the coalescence of interaction regions and (2) a transfer of energy from the spectrum of large-scale speed fluctuations. The outer cutoff of the spectrum of speed fluctuations increases from a period of 13 days at 1 AU to 26 days between a few AU and 8.9 AU. Both the magnetic field strength fluctuations and the speed fluctuations have fractal behavior, suggesting that they are self affine rather than dominated by a few large discontinuities.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 1261-126
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  • 32
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    Highlights of the study of energy release in flares (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: From February 26 to March 1, 1979, 32 solar flare investigators attended a workshop at Cambridge, MA to define objectives and devise a scientific program for the study of energy release in flares (SERF) during the coming solar maximum. Herein, some major results of the ensuing five-year effort to observe and understand the flare energy release process and its effects (energetic particle production, coronal and chromospheric heating, electromagnetic radiations, and mass motions and ejections) are reviewed. The central issue - what processes store and release the energy liberated in flares - remains unresolved except in the most general terms (e.g., it is generally agreed that the energy is stored in sheared or stressed magnetic fields and released by field annihilation during some MHD instability). Resolving that issue is still one of the most important goals in solar physics, but the advances during the SERF program have brought it closer.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 114; 2, 19
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    On the distribution of sunspot cycle periods (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A comparison is made between the observed distribution of sunspot cycle periods and distributions based on uniform, normal, and bimodal distributions. The bimodal distribution, composed of short-period and long-period cycles, is found to best describe the observed distribution. Compared to the normal distribution for the most reliably determined cycles (cycles 8-20), the bimodal distribution has a residual (sum of squares of differences) that is about 86 percent smaller. Means for short-period and long-period cycles are estimated to be 122 + or - 4 months and 140 + or - 5 months, respectively.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 10
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    Sunspot umbral oscillations in Mg II k (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Time series observations of the profile of the Mg II k line 2795.52 A have been obtained in five sunspots with the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission. The three sunspots with umbrae larger than the 3 x 3 arcsec pixel size show significant oscillations in integrated line intensity and line centroid, with frequencies in the range 5.29-7.55 mHz (periods of 132-190 s). The frequencies of significant peaks in average umbral power spectra agree well with the frequencies of the three lowest-frequency transmission peaks predicted by a model of resonant transmission of acoustic waves. If radiative delays are unimportant, and the line centroid can be interpreted straightforwardly as a Doppler shift, the measured velocity-intensity phase differences indicate the superposition of upward-propagating and downward-propagating waves in the umbral chromosphere; this is further evidence for the resonant transmission model. A single, quiet sun time series of k core profiles yields power spectra and a phase difference consistent with the existence of a chromospheric p-mode.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 108; 1, 19
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  • 35
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    Kinetics of mineral condensation in the solar nebula (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A natural extension of the type of gas-mineral-melt condensation experiments is to study the gas-mineral-melt reaction process by controlling the reaction times of appropriate gas compositions with silicate materials. In a condensing and vaporizing gas-solid system, important processes that could influence the composition of and speciation in the gas phase are the kinetics of vaporization of components from silicate crystals and melts. The high vacuum attainable in the space station would provide an environment for studying these processes at gas pressures much lower than those obtainable in experimental devices operated at terrestrial conditions in which the gas phase and mineral or melt would be allowed to come to exchange equilibrium. Further experiments would be performed at variable gas flow rates to simulate disequilibrium vapor fractionation. In this type of experiment it is desirable to analyze directly the species in the gas phase in equilibrium with the condensed silicate material. This analytical method would provide a direct determination of the species present in the gas phase. Currently, the notion of gas speciation is based on calculations from thermodynamic data. The proposed experiments require similar furnace designs and use similar experimental starting compositions, pressures, and temperatures as those described by Mysen.
    Keywords: SOLAR PHYSICS
    Type: NASA, Lyndon B. Johnson Space Center, Experiments in Planetary and Related Sciences and the Space Station; 2 p
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  • 36
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    Large-scale horizontal flows from SOUP observations of solar granulation (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Using high resolution time sequence photographs of solar granulation from the SOUP experiment on Spacelab 2, large scale horizontal flows were observed in the solar surface. The measurement method is based upon a local spatial cross correlation analysis. The horizontal motions have amplitudes in the range 300 to 1000 m/s. Radial outflow of granulation from a sunspot penumbra into surrounding photosphere is a striking new discovery. Both the supergranulation pattern and cellular structures having the scale of mesogranulation are seen. The vertical flows that are inferred by continuity of mass from these observed horizontal flows have larger upflow amplitudes in cell centers than downflow amplitudes at cell boundaries.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 121-127
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  • 37
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    Loop interaction in the visible emission corona: Morphological details (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Coronagraph observations of two post flare loop systems, recorded photographically in the emissions of Fe 14 (5303 A) and Fe 10 (6374 A), show occasional enhancements at the intersections of some loops. The brightness of such enhancements in the green line gradually increases to a maximum value several times greater than that of the legs of the loops and then declines with a typical lifetime approx. 30 to 60 min. In red line emission the loop systems are usually very faint, but show the same overall type of enhancement, with a lag in maximum brightness relative to that of the green line approx. 10 min. The electron density, derived from the cooling time, is approx. 10 to the 12th power/cu cm.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 129-132
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  • 38
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    Solar transition region and coronal response to heating rate perturbations (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The solar transition region is in a dynamic state characterized by impulsively upflowing plasma and continually downflowing plasma. Using numerical simulations, the conjecture that the areas of downflowing plasma are simply the base regions of coronal loops in which the heating rate is gradually decreasing and the areas of upflowing plasma are the base regions of coronal loops in which the heating rate is gradually increasing is examined. The calculations suggest that gradually reducing or increasing the heating in a magnetic flux tube will not result in plasma motions that are similar to those that are observed at high spatial resolution in the UV.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 117-119
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  • 39
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    Pressure structure of solar coronal loops (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The steady state pressure structure of a coronal loop is discussed in terms of the MHD global invariants of an incompressible plasma. The steady state is represented by the superposition of two Chandrasekhar-Kendall functions corresponding to (n=m=0) and (n=m=1) modes. The relative contribution of the two modes (epsilon) is found to depend on the surface pressure of the coronal loop which is also the pressure of the external medium. The mixed mode state does not exist for high values of the external pressure because epsilon becomes complex.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 107-111
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  • 40
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    A numerical study of the thermal stability of solar loops (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An important property of all loops is their thermal stability. If low lying hot loops were thermally unstable, for example, a great majority of the low loops on the Sun might be expected to be cool. How small perturbations evolve in low lying, linearly unstable hot loops was determined and how high lying, linearly stable hot loops respond to large amplitude disturbances such as might be expected on the Sun were examined. Only general descriptions and results are given.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 113-116
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  • 41
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    Theoretical modelling of the fine structures in sunspots (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Until a decade ago most solar physicists thought of a sunspot as the upper end of a giant flux tube floating vertically. The existence of umbral dots and penumbral grains has been known for several decades. On the basis of available observations, they seem to be regions of photospheric intensity with upflowing gas motion and magnetic fields much weaker than in the surrounding sunspot surface. It has also been suggested that the differences in the appearances of umbral dots and granular cells are caused by the highly nonlinear nature of the convection problem in the presense of strong magnetic fields. The main ideas are presented here without any equations. It can be shown that a pocket of field free gas surrounded by a vertical magnetic field in the presence of gravity takes up the shape of a tapering column ending at a vertex at the top. Some convection is expected to take place in the trapped field free gas, whereas the magnetic field around it makes those regions stable against convection. Eventually the apex of the tapering column reaches the photospheric surface where the bulging of the magnetic field makes the field no longer able to close on the field free gas and trap it underneath.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 105-106
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  • 42
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    High-resolution continuum observations of the Sun (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The aim of the PFI or photometric filtergraph instrument is to observe the Sun in the continuum with as high resolution as possible and utilizing the widest range of wavelengths. Because of financial and political problems the CCD was eliminated so that the highest photometric accuracy is only obtainable by comparison with the CFS images. Presently there is a limitation to wavelengths above 2200 A due to the lack of sensitivity of untreated film below 2200 A. Therefore the experiment at present consists of a film camera with 1000 feet of film and 12 filters. The PFI experiments are outlined using only two cameras. Some further problems of the experiment are addressed.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 79-88
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    What's needed in the UV and EUV (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: High spectral and spatial resolution UV and EUV spectroscopy is discussed with emphasis on the spectroscopic observations that are required in order to increase the understanding of the physics of the lower transition region. The properties of the lower transition region are reviewed, and the available lower transition region plasma diagnostics are reviewed for the wavelength range between about 1150 and 2000 A. One important conclusion is that comprehensive spectroscopic coverage over a rather broad temperature range is necessary in order to observe satisfactorily small transition region structures. This is illustrated by two examples from the recent NRL Spacelab 2 HRTS experiment.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 37-54
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  • 44
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    Magnetic field morphology in the upper layers (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Some basic properties of emerged magnetic flux concentrations are examined with emphasis on the interplay between the magnetic and thermodynamic structure in the region between the photosphere and the transition zone. The discussion is limited to the gross behavior of those phenomena that may be reasonably regarded as quasi-static, such as the longer-lived sunspots, pores, and some smaller magnetic flux tubes. Substructure and dynamic phenomena are not considered.
    Keywords: SOLAR PHYSICS
    Type: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 1-13
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  • 45
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    An account of a flare related shock event recorded by the energetic particle detector EPONA of the Giotto spacecraft during September 1985 (STIP interval 18) (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Energetic Particle Detector EPONA flown on the Giotto Mission to Halley's Comet was designed to measure electrons, protons, and heavier ions (E greater that 20 keV) in the Comet Halley environment and during the Cruise Phase of the mission (EPONA switch on: 22 August 1985 - Halley encounter: 13 March 1986). In September 1985 (STIP Interval XVIII) a well defined shock event was recorded at EPONA in association with a sequence of solar flares and a preliminary account of this event is presented.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 56
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    Solar prediction and intelligent machines (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The solar prediction program is aimed at reducing or eliminating the need to throughly understand the process previously developed and to still be able to produce a prediction. Substantial progress was made in identifying the procedures to be coded as well as testing some of the presently coded work. Another project involves work on developing ideas and software that should result in a machine capable of learning as well as carrying on an intelligent conversation over a wide range of topics. The underlying idea is to use primitive ideas and construct higher order ideas from these, which can then be easily related one to another.
    Keywords: SOLAR PHYSICS
    Type: NASA. Lyndon B.; NASA. Lyndon B. John
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  • 47
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    The temperature of solar flares determined from X-ray spectral line ratios (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The effect on derived solar flare plasma temperatures of (1) a power-law distribution of emission measure as a function of temperature, (2) a high-temperature isothermal source coupled to a low-temperature power-law distribution of emission measure, and (3) two isothermal sources is calculated for line ratios involving the ions S XV, Ca XIX, Ca XX, Fe XXV, Ni XXVII, and Fe XXVI. It is shown that if the Fe XXV temperature is less than about 25 million K, as is true for the majority of flares, then about 75 percent or more of the emission measure is produced by plasma at temperatures equal to or less than the Fe XXV temperature plus about 3 million K. If the Fe XXV temperature is 20 million K or higher, this percentage can be larger. This result is obtained even if a superhot component exists that extends up to several hundred million degrees. Temperatures determined from Fe XXVI demonstrate the presence of a superhot component.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 313; 883-892
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    Ultraviolet Al III emission lines and the physics of the solar transition region (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Two lines of the solar UV spectrum were identified as due to 3p-3d Al III transitions near 1612 A; the ratios of these lines to the 3s-3p Al III doublet near 1855 A were found to be very sensitive to temperature. Thus, the temperatures of formation of the Al III lines could be determined by using one of the line ratios in two quiet sun regions, a coronal hole, and an active region. The results were found to be consistent with expectations based on the assumption of ionization equilibrium for Al III. It is suggested that S III lines near 1350 A and 1200 A may also serve as a temperature diagnostic.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 315; L67-L70
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  • 49
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    Viscous damping of Alfven normal modes in non-uniform plasmas (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Alfven normal mode in a nonuniform, viscous plasma is investigated. Because the ideal hydromagnetic equation is singular in a nonuniform magnetic field, viscosity is included in order to regularize the equation, analogous to the removal of the singular point by resistivity (Mok and Einaudi, 1985). The eigenvalue equation is then solved numerically for a particular magnetic configuration. The real part of the frequency of this viscous normal mode is found to be similar to the one in the resistive case, while the damping is shown to be comparable, and sometimes to exceed, the resistive effect under certain conditions in which the Lundquist number is sufficiently large. The damping rate is evaluated for various plasma conditions corresponding to different parts of the solar atmosphere. The effects of viscosity are found to dominate resistivity in the quiet sun corona and solar wind.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 172; 1-2,; 327-331
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  • 50
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    Dynamics of solar filaments. V - Oscillations in the H-alpha and 1548 A C IV lines (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Multichannel Subtractive Double Pass (MSDP) Spectrograph operating in the Meudon solar tower and the Ultraviolet Spectrometer and Polarimeter (UVSP) aboard the Solar Maximum Mission (SMM) satellite are used to analyze, by Fourier transform technique, time sequence observations of filaments in both the H-alpha line and in the 1548 A C IV line. The H-alpha data confirm previous findings that there are no oscillations at the location of the filament in the observed range 1-10 mHz. In the C IV line, power is observed in some parts of the filament where a steady velocity gradient is present, e.g. in the footpoints. The energy is probably due to convection motions rather than pressure oscillations.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 172; 1-2,
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    Effects of non-Maxwellian electron velocity distribution functions and nonspherical geometry on minor ions in the solar wind (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A previous model has shown that in order to account for the charge state distribution in the low-speed solar wind, a high coronal temperature is necessary and that this temperature peak goes together with a peak of nx/np in the corona. In the present paper, one of the assumptions made previously, i.e., that coronal electrons are Maxwellian, is relaxed, and a much cooler model is presented, which could account for the same oxygen charge states in the solar wind due to the inclusion of non-Maxwellian electrons. Also, due to a different choice of the coronal magnetic field geometry, this model would show no enhancement of the coronal nx/np. Results of the two models are then compared, and observational tests to distinguish between the two scenarios are proposed: comparison of directly measured coronal Te to charge state measurements in the solar wind, determination of the coronal nx/np measurement of ion speeds in the acceleration region of the solar wind, and measurement of the frozen-in silicon charge state distribution.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 1057-106
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  • 52
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    A numerical study of transient, thermally-conductive solar wind (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A numerical analysis of transient solar wind starting at the solar surface and arriving at 1 AU is performed by an implicit numerical method. The model hydrodynamic equations include thermal conduction terms for both steady and unsteady simulations. Simulation results show significant influence of thermal conduction on both steady and time-dependent solar wind. Higher thermal conduction results in higher solar wind speed, higher temperature, but lower plasma density at 1 AU. Higher base temperature at the solar surface gives lower plasma speed, lower temperature, but higher density at 1 AU. Higher base density, on the other hand, gives lower velocity, lower temperature, but higher density at 1 AU.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 33
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    Solar activity, magnetic clouds, and geomagnetic storms (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Associational aspects of magnetic clouds and solar activity, and of magnetic clouds and geomagentic storms are described. For example, recent research has shown associations to exist between the launch of magnetic clouds directed Earthward from the Sun and, in particular, two forms of solar activity: flare-related, type II metric radio bursts and disappearing filaments (prominences). Furthermore, recent research has shown an association to exist between the onset of magnetic clouds on Earth and the initiation of geomagnetic storms. Based on these findings, STIP Intervals XV-XIX are examined for possible occurrences of Earthward-directed magnetic clouds.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 30
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    Was the eclipse comet of 1893 a disconnected coronal transient? (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The comet-like feature obsereved in the solar corona by the Lick Observatory eclipse expedition to Chile in 1893 bears an interesting resemblance to the disconnection coronal transient reported by Illing and Hundhausen. Reports of possibly-related limb activity are reviewed to see whether a pre-discovery observation of a relatively rare type of coronal mass ejection was mis-interpreted. The goal of this study is to learn more about the morphology of mass ejections by examining observations that extend down to the low corona of a disconnection event.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 27
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    Solar events and their influence on the interplanetary medium (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Aspects of a workshop on Solar events and their influence on the interplanetary medium, held in September 1986, are reviewed, the goal of which was to foster interactions among colleagues, leading to an improved understanding of the unified relationship between solar events and interplanetary disturbances. The workshop consisted of three working groups: (1) flares, eruptives, and other near-Sun activity; (2) coronal mass ejections; and (3) interplanetary events. Each group discussed topics distributed in advance. The flares-eruptives group members agreed that pre-event energy is stored in stressed/sheared magnetic fields, but could not agree that flares and other eruptive events (e.g., eruptive solar prominences) are aspects of the same physical phenomenon. In the coronal mass ejection group, general agreement was reached on the presence of prominences in CMEs, and that they have a significant three-dimensional structure. Some topics identified for further research were the aftermath of CMEs (streamer deflections, transient coronal holes, possible disconnections), identification of the leading edge of CMEs, and studies of the range and prevalence of CME mass sizes and energies.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 29
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    Coronal and interplanetary Type 2 radio emission (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Several observations suggest that the disturbances which generate coronal (meter wavelength) type II radio bursts are not driven by coronal mass ejections (CMEs). A new analysis using a large sample of metric radio bursts and associated soft X-ray events provides further support for the original hypothesis that type II-producing disturbances are blast waves generated at the time of impulsive energy release in flares. Interplanetary (IP) shocks, however, are closely associated with CMEs. The shocks responsible for IP type II events (observed at kilometer wavelengths) are associated with the most energetic CMEs.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 25
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    Coronal mass ejections: The long-term variation of their occurrence rate and the solar wind mass flux (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Solar Coronal Mass Ejections (CMEs) from the Sun are an important aspect of coronal physics, and a potentially important contributor to the solar wind mass flux. However, despite significant progress in studies of CMEs since their discovery in the early 70's, questions remain about their effects on the interplanetary medium. A study is done of the long-term variations of the occurrence rates of CMEs, of activity tracers related to CMEs, and of the solar wind particle flux. CMEs are most directly detected by scattered electron radiation in white light. To estimate their long-term occurrence frequency and their contributions to the in-ecliptic solar wind mass flux, observed CME rates must be corrected for instrumental duty cycles, detection efficiency out of the plane of the sky, mass detection thresholds, and geometrical considerations. These corrections are evaluated using data on solar CMEs from the spaceborne Skylab, SMM, and SOLWIND coronagraphs and on interplanetary plasma clouds from the HELIOS white light photometers. Variations in the CME rate and the contribution of CMEs to the solar wind mass flux are traced over nearly a complete solar activity cycle.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 26
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    Observations of the brightness temperature distribution of the quiet solar corona at decametric wavelengths (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The brightness temperature distribution of the quiet solar corona at a wavelength of 8.9 meters is measured by two types of radio telescope: (1) a 'T' type array with a resolution of 26'X38', and (2) a fan beam interferometer with an E-W resolution of 3'. It is found that the persistent bright regions do not have any angular structure on scales of 6' or less. The daily variations of the brightness temperature of different regions are studied and the possible interpretation discussed.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 23
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  • 59
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    Meterwave observations of a coronal hole (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Meter-wave maps are presented showing a coronal hole at 30.9, 50.0, and 73.8 MHz using the Clark Lake Radioheliograph in October 1984. The coronal hole seen against the disk at all three frequencies shows interesting similarities to, and significant differences from its optical signatures in HeI lambda10830 spectroheliograms. The 73.8 MHz coronal hole, when seen near disk center, appears to coincide with the HeI footprint of the hole. At the lower frequencies, the emission comes from higher levels of the corona, and the hole appears to be displaced, probably due to the non-radial structure of the coronal hole. The contrast of the hole relative to the quiet Sun is much greater than reported previously for a coronal hole observed at 80 MHz. The higher contrast is certainly real, due to the superior dynamic range, sensitivity, and calibration of the Clark Lake instrument. Using a coronal hole model, the electron density is derived from radio observations of the brightness temperature. A very large discrepancy is found between the derived density and that determined from Skylab EUV observations of coronal holes. This discrepancy suggests that much of the physics of coronal holes has yet to be elucidated.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 24
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  • 60
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    Radio studies of large scale structures of the Sun's corona and transient activity (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The use of meter-decimeter wavelength imaging observations for four different kinds of studies of solar coronal activity is discussed. (1) Large scale structure of the upper corona; daily imaging observations permit comparison of radio images with white light images from space and ground observation, generation of synoptic charts similar to white light coronagraph synoptic charts, and comparison of radio brightness enhancements and deficiencies with bright coronal streamers and coronal holes. (2) Relative positions of type III burst sources and coronal streamers as observed by Solwind experiment on the P-78-1 satellite and by the HAO C/P experiment aboard the SMM; infer the paths of type III emitting electrons in dense coronal streamers, and from multifrequency observations derive electron density distributions above active regions near the limb. (3) Non-flare associated type II/type IV bursts associated with coronal streamer disruption events; such type IV sources have a rather slow velocity (approx = to or less than 100 km/s) CMEs. (4) Meter-decimeter microbursts; these are short duration (2-10 sec) weak-type III-like bursts, produced at the fundamental plasma frequency by plasma radiation processes which have important differences from the standard mechanisms used to explain the strong type III bursts.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 22
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  • 61
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    On the association of erupting magnetic fields with eruptive prominences and coronal mass ejections (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A number of space and ground-based observations give evidence that the eruptive prominences, coronal mass ejections (CMEs) and associated shocks are generated by a common cause, i.e., the eruption of the magnetic field on the Sun. Some 60% of the observed CMEs are associated with the eruptive prominences. It is believed that in reality a much better correlation should be between these events because of observational limitations and of the effect of partial eruption. Some recent results on the formation and evolution of the quiescent and the active region prominences give an idea on the early phase of eruption of the magnetic field with the prominence plasma frozen in. In the latter phase of eruption the magnetic field lifted high into the corona and is seen (as manifested by the cold plasma frozen in) as a system of huge loops - evidently the result of some reconnections at lower heights. The legs of these erupting loops interact sometimes with the local magnetic field, i.e., it often appears to be an active region. In consequence of this interaction the activation of prominences and generation of flares can take place on some occasions as well as ejection of surges and sprays.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 21
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  • 62
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    Solar origins of coronal mass ejections (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The large scale properties of coronal mass ejections (CMEs), such as morphology, leading edge speed, and angular width and position, have been cataloged for many events observed with coronagraphs on the Skylab, P-78, and SMM spacecraft. While considerable study has been devoted to the characteristics of the SMEs, their solar origins are still only poorly understood. Recent observational work has involved statistical associations of CMEs with flares and filament eruptions, and some evidence exists that the flare and eruptive-filament associated CMEs define two classes of events, with the former being generally more energetic. Nevertheless, it is found that eruptive-filament CMEs can at times be very energetic, giving rise to interplanetary shocks and energetic particle events. The size of the impulsive phase in a flare-associated CME seems to play no significant role in the size or speed of the CME, but the angular sizes of CMEs may correlate with the scale sizes of the 1-8 angstrom x-ray flares. At the present time, He 10830 angstrom observations should be useful in studying the late development of double-ribbon flares and transient coronal holes to yield insights into the CME aftermath. The recently available white-light synoptic maps may also prove fruitful in defining the coronal conditions giving rise to CMEs.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 20
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    Study of pickup of cometary ions in turbulent solar winds (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The influence of moderately strong magnetic disturbances on the ion pickup process near a comet is studied by a test-particle method. The research is motivated by recent observations with ICE and Giotto at Giacobini-Zinner and Halley. In this numerical study, the intrinsic hydromagnetic turbulence is modelled based on the Giotto and ICE data. The time evolution of the distribution function of the newborn ions is investigated. It is found that, when the level of the intrinsic turbulence is sufficiently high, the pickup ions can form a shell distribution function rapidly. The typical time scale for such a process is of the order of a couple of ion gyroperiods. On the other hand, if the turbulence is not strong, the pickup ions usually form an incomplete shell in the initial stage. The results seem to be consistent with available observations.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 18
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  • 64
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    Magnetic field twist driven by remote convective motions: Characteristics and twist rates (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: It is generally believed that convective motions below the solar photosphere induce a twist in the coronal magnetic field as a result of frozen-in physics. A question of interest is how much twist can one expect from a persistent convective motion, given the fact that dissipative effects will eventually figure. This question is examined by considering a model problem: two conducting plates, with finite resistivity, are set in sheared motion and forced at constant relative speed. A resistive plasma is between the plates and an initially vertical magnetic field connects the plates. The time rate of tilt experienced by the field is obtained as a function of Hartmann number and the resistivity ratio. Both analytical and numerical approaches are considered.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 17
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  • 65
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    Comparison of MHD simulation for the February 1986 events with interplanetary observations by the spacecraft Sakigake (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: During the period 3-10 February 1986 a series of major solar flares occurred on the Sun and several intense geomagnetic storms took place on the Earth. To examine the causality between the solar activity and the geomagnetic activity in this period, a magnetohydrodynamic (MHD) numerical simulation was performed using a 2 1/2 -D numerical code. In that period of February 1986, the Japanese spacecraft Sakigake was at 0.84 AU, 57 deg west of the Earth. Besides the in-situ measurements of the interplanetary plasma, Sakigake also provided Doppler scintillation observations. Comparisons between the results of the MHD simulation and the measurements made by the spacecraft Sakigake are presented.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 15
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  • 66
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    Two dimensional imaging observations of meter-decameter bursts associated with the February 1986 flare activity (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An analysis is presented of the two dimensional imaging observations of a flare observed on 3 Feb. l986 using the Clark Lake Multifrequency Radioheliograph. The flare produced almost all types of Meter-decimeter radio emission: enhanced storm radiation, type III/V bursts, II and IV and flare continuum. The flare continuum had early (FCE) and late (FC II) components and the type II occurred during the period between these two components. Comparing the source positions of type III/V and FCE it was found that these bursts must have occurred along adjacent open and closed field lines, respectively. The positional analysis of type II and FC II implies that the nonthermal electrons responsible for FC II need not be accelerated by type II shock and this conclusion is further supported by the close association of FC II with a microwave peak. Using the positional and temporal analysis of all these bursts and the associated hard X-ray and microwave emissions, a schematic model is developed for the magnetic field configuration in the flaring region in which the nonthermal particles responsible for these bursts are confined or along which they propagate.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 16
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  • 67
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    Evolution of the solar wind structure in the outer heliosphere (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Shocks and interaction regions play very important roles in the evolution of large-scale solar wind structure in the outer heliosphere. This study is based on (1) plasma and magnetic field data observed from Voyager and Pioneer spacecraft, and (2) a quantitative magnetohydrodynamic simulation model. Interaction regions bounded by a forward and a reverse shock begin to form near 1 AU at the leading edges of a large-scale stream. The total pressure in the region is greater than the ambient pressure by a factor of ten or more. Large jumps in pressure remain as a prominant feature of the interplanetary structure even as the jumps in flow speed become less visible in the outer heliosphere. The propagation of the forward and reverse shocks widens the dimension of an interaction region. As a result, two interaction regions belonging to neighboring streams coalesce to form a merged interaction region (MIR). Collision and merging of shocks take place during the coalescence process. Two MIRs can themselves merge again at greater heliocentric distances. Simulation results agree well with spacecraft observations, and they explain major restructuring of the solar wind in the outer heliosphere.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 14
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  • 68
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    Solar modulation of the cosmic radiation in the heliosphere (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Changes in the solar modulation of galactic and anomalous component cosmic rays reflect changes in the structure and magnetic topology of the interplanetary medium. Therefore, to the extent that the modulation process is understood, the cosmic rays can be used as a probe of the medium to infer the extent and structure of the heliosphere in regions not directly sampled by spacecraft. The challenge to modulation theory and observation has been to determine which properties of the solar wind are most important for producing the observed modulation. Significant progress has been made in answering this question during the last solar cycle using observations from spacecraft at radii to 40 AU from the Sun and at latitudes up to 30 degrees with respect to the ecliptic. A brief summary of new results and observations (with specific attention to the STIP intervals XV-XIX) will be presented to illustrate the present state of our understanding of the relation between the solar wind and interplanetary magnetic field and the modulations of the cosmic radiation.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 13
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  • 69
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    Change in interplanetary shock acceleration preceding STIP Interval 17 (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The intensity and frequency of shock acceleration events in the interplanetary medium decreased dramatically in early 1985. Low energy ions were observed by IMP 8 at 1 AU and Voyagers 1 and 2 at 22 and 16 AU, respectively. Voyager 1 was at 25 deg heliographic latitude while IMP 8 and Voyager 2 were near the solar equatorial plane. The decrease in low energy shock events led to a drop in the average ion flux by a factor of 20 to 50. It started about day 10 of 1985 in the approximately .5 MeV channel on IMP8 and took approximately 75 days to reach the new, lower, background level. The decrease at the Voyagers started approximately 50 days later. The time delay between the start of the decrease at IMP and at Voyager 2 implies that decrease was convected outward with a velocity of approximately 535 km/sec. The intensity and frequency of interplanetary shock events remained at the lower level for at least 1.5 years.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 12
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  • 70
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    Propagating shocks in the corona (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: High resolution observations performed with the Decimeter spectrograph and the multichannel receiver at Nancay were analyzed in the range of 25-75 MHz. Sixty Type II bursts were selected. In this frequency range, type II events are generally associated with other radio emissions (such as storms of type III-U-I bursts); they are preceeded or followed by groups of U-bursts. One third of type II events show a nonuniform frequency drift, usually a steep decrease followed by an abrupt increase. This phenomenon can be explained by the propagation of an extended disturbance through the ambient corona when the density gradient is enhanced. An empirical coronal model is proposed to interpret these observations. The observations at fixed frequency of Type II bursts including fundamental and harmonic components are analyzed. It is shown that the spectrum of the intensity fluctuations differs with the fundamental and the harmonic components. The origin of these differences is discussed.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 11
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  • 71
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    Protostellar disks and the primitive solar nebula (1987)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The objective is to obtain quantitative information on the turbulent transport of mass, angular momentum, and energy under the conditions that characterize the solar nebula, by direct numerical calculations. These calculations were made possible by research conducted on supercomputers (Cray XMP and Cray 2) by the Ames Computational Fluid Dynamics Branch. Techniques were developed that permitted the accurate representation of turbulent flows over the full range of important eddy sizes. So far, these techniques were applied (and verified) primarily in mundane laboratory situations, but they have a strong potential for astrophysical applications. A sequence of numerical experiments were conducted to evaluate the Reynold's stress tensor, turbulent heat transfer rate, turbulent dissipation rate, and turbulent kinetic energy spectrum, as functions of position, for conditions relevant to the solar nebula. Emphasis is placed on the variation of these properties with appropriate nondimensional quantities, so that relations can be derived that will be useful for disk modeling under a variety of hypotheses and initial conditions.
    Keywords: SOLAR PHYSICS
    Type: NASA, Washington, Reports of Planetary Geology and Geophysics Program, 1986; p 97-99
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  • 72
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    Interactions of oblique interplanetary discontinuities and their manifestations during STIP intervals 15-19 (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The generation of slow shock waves as the result of the interaction of Alfven discontinuities with solar wind contact surfaces is considered. The latter are taken to be the boundaries of proton and alpha-particle concentration inhomogeneities. It is found that the intensity of the Alfven discontinuity may be increased as the result of its interaction with the more dense plasma. The converse (i.e., decrease of the Alfven discontinuity's intensity following interaction with a less dense plasma) is also indicated. Also discussed is the generation of a magnetic cloud as the result of the interaction of a quasi-parallel Alfven discontinuity with a dense plasma contact surface. It is shown that the (solar-generated) Alfven discontinuity may then be transformed into non-flare fast and slow shock waves as the result of this interaction. Thus, it is indicated that some fast shock waves in the solar wind may have a nonsolar origin.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 57
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  • 73
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    Study of the mechanism for solar wind formation (1987)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Observations of the corona and solar wind are analyzed and compared with generalized results derived from laboratory-scale experiments. It was shown that a thermal pressure gradient can make a major contribution to a precipitating plasma of the solar wind emanating from coronal holes. It is found that the divergence Phi = (R/R sub solar radius)f of the magnetic field lines, originating from coronal holes, is one of the factors governing solar wind velocity at Earth orbit (R= 1 AU). A decrease in the velocity V sub R = 1 AU from approx = 750 mk/sec down to approx = 450 km/sec may be attributable to an increase in superradial divergence f from approx = 7-9 to 20. The plasma energy flux density F at the base of the coronal holes representing the sources of the solar wind with V sub R=1AE = (450 to 750) km/sec, remains nearly constant, being F approx = (1.4 +/- 0.3) x 10 to the 6th power x ergs/sq cm/sec for the period 1973-1975.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 55
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  • 74
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    NASA/MSFC prediction techniques (1987)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The NASA/MSFC method of forecasting is more formal than NOAA's. The data is smoothed by the Lagrangian method and linear regression prediction techniques are used. The solar activity period is fixed at 11 years--the mean period of all previous cycles. Interestingly, the present prediction for the time of the next solar minimum is February or March of 1987, which, within the uncertainties of two methods, can be taken to be the same as the NOAA result.
    Keywords: SOLAR PHYSICS
    Type: Upper and Middle Atmospheric Density Modeling Requirements for Spacecraft Design and Operations; p 151-153
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  • 75
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    Forecasts of solar and geomagnetic activity (1987)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Forecasts of solar and geomagnetic activity are critical since these quantities are such important inputs to the thermospheric density models. At this time in the history of solar science there is no way to make such a forecast from first principles. Physical theory applied to the Sun is developing rapidly, but is still primitive. Techniques used for forecasting depend upon the observations over about 130 years, which is only twelve solar cycles. It has been noted that even-numbered cycles systematically tend to be smaller than the odd-numbered ones by about 20 percent. Another observation is that for the last 12 cycle pairs, an even-numbered sunspot cycle looks rather like the next odd-numbered cycle, but with the top cut off. These observations are examples of approximate periodicities that forecasters try to use to achieve some insight into the nature of an upcoming cycle. Another new and useful forecasting aid is a correlation that has been noted between geomagnetic indices and the size of the next solar cycle. Some best estimates are given concerning both activities.
    Keywords: SOLAR PHYSICS
    Type: NASA. Marshall Space Flight Center Upper and Middle Atmospheric Density Modeling Requirements for Spacecraft Design and Operations; p 141-149
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    The topology of force-free magnetic fields and its implications for coronal activity (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The topological constraints on coronal magnetic fields are considered. For a field that is initially well-behaved and undergoes deformation by well-behaved ideal MHD motions, it is shown that the topology of the field lines in the corona can be determined at all times solely from the footpoint positions on the photospheric boundary. This result implies that the topology and, consequently, the history of the footpoint motions impose no further constraints on the field beyond those already included in the connectivity boundary conditions, so that there is no reason to expect a lack of equilibrium for fields that are initially well-behaved and evolve by ideal MHD. On the other hand, nonideal processes such as reconnection are bound to occur in the solar corona, and these may lead to magnetic topologies that have no well-bahaved Euler potentials. Hence Parker's hypothesis that footpoint motions lead to the formation of current sheets is still likely to be correct, but only if nonideal processes are included. The effects of reconnection on magnetic topology and the implications for coronal activity are discussed.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 312; 886-894
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    Nuclear processes and accelerated particles in solar flares (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Nuclear processes and particle acceleration in solar flares are discussed and the theory of gamma-ray and neutron production is reviewed. Gamma-ray, neutron, and charged-particle observations of solar flares are compared with predictions, and the implications of these comparisons for particle energy spectra, total numbers, anisotropies, electron-to-proton ratios, and acceleration mechanisms are considered. Elemental and isotopic abundances of the ambient gas derived from gamma-ray observations have also been compared to abundances obtained from observations of escaping accelerated particles and other sources.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 113; 1-2,; 203-213;
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  • 78
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    Ion and relativistic electron acceleration by Alfven and whistler turbulence in solar flares (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A model is proposed in which turbulent Alfven and whistler waves simultaneously produce the proton and electron spectra implied by the gamma-ray observations noted during the impulsive phase of the June 3, 1982 flare. The results demonstrate that protons can be accelerated to several GeV in less than about 10 sec by Alfven turbulence whose energy density is greater than a few erg/cu cm. It is also found that electrons may be accelerated to tens of MeV on similar time scales by whistler and Alfven turbulence. A lower limit on the energy density of the Alfven turbulence is obtained which is small compared to the total magnetic energy density.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 113; 1-2,; 195-200;
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  • 79
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    Origin and evolution of fluctuations in the solar wind - Helios observations and Helios-Voyager comparisons (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Hour-averaged data from the Helios and Voyager spacecraft are used here to investigate the origin and evolution of low-frequency interplanetary fluctuations from 0.3 to 20 AU. The previously observed evolution toward a less purely Alfvenic state with increasing heliocentric distance is shown to occur more rapidly in the inner heliosphere and in low-speed as well as high-speed streams. It is concluded that outward-traveling flucutations are predominantly generated by the sun, but that in situ turbulence, most likely due to stream shear, generates fluctuations with both inward and outward senses of correlation.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 12023-12
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    ISEE 3 observations of low-energy proton bidirectional events and their relation to isolated interplanetary magnetic structures (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The paper represents the results of a comprehensive survey of low-energy proton bidirectional anisotropies and associated transient magnetic structures as observed in the 35-1600 keV energy range on ISEE-3 during the last solar maximum. The majority of observed bidirectional flow (BDF) events (more than 70 percent) are associated with isolated magnetic structures which are postulated to be an interplanetary manifestation of coronal mass ejection (CME) events. The observed BDF events can be qualitatively grouped into five classes depending on the field signature of the related magnetic structure and the association (or lack of association) with an interplanetary shock. Concerning the topology of the CME-related magnetic structures, the observations are interpreted as being consistent with a detached bubble, comprising closed loops or tightly wound helices.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 11009-11
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  • 81
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    Is solar neutrino capture rate correlated with sunspot number? (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The statistical significance of the apparent correlation between sunspots and the observed neutrino rate is quantified. It is shown that the correlation depends almost entirely upon four low neutrino capture rates near the beginning of 1980. A calculation based on standard electroweak theory and neutrino production processes demonstrates that a correlation, if real, would be extremely puzzling on energetic grounds alone. It is concluded that measurements with the Cl-37 detector during the next sunspot cycle will be needed to show that there is a physical correlation, since the existing data are not statistically significant at a definitive level.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 320; L69-L73
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  • 82
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    A numerical study of the nonlinear thermal stability of solar loops (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A time-dependent numerical model is used to investigate the nonlinear thermal stability of static loops of various heights. Simulations show that the instability of a hot state with loop heights of less than about 1000 km is physically significant, with an initially hot atmosphere in low-lying compact loops evolving to an extended atmosphere with temperatures far below 100,000 K. Results also show that high-lying loops are stable to all reasonable perturbations, including those of large initial amplitude and long wavelength. The simulation results suggest that low-lying compact loops should not be common to the sun, and that cool loops with temperatures near 100,000 K must be formed in the cool state initially and cannot evolve from preexisiting loops.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 320; 409-417
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  • 83
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    Solar transition region and coronal response to heating rate perturbations (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of Doppler shifts in UV emission lines formed in the solar transition region show continual plasma downflows and impulsive plasma upflows. Using numerical simulations, the authors examine the conjecture that areas of downflowing plasma are the base regions of coronal loops in which the heating is gradually decreasing and that areas of upflowing plasma are the base regions of coronal loops in which the heating rate is gradually increasing. Beginning with a coronal loop in equilibrium, the heating rate is reduced on time scales of 100, 1000, and 2000 s to 10 percent and 1 percent of the initial value, and the loop is allowed to evolve to a new equilibrium. The heating rate for the cooled models is then increased back to the initial value on the same time scales. While significant mass motions do develop in the simulations, both the emission measure and the velocity at 100,000 K do not show the characteristics present in UV observations.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 319; 465-480
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  • 84
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    Observation of nonthermal energy distributions during the impulsive phase of solar flares (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Fe XXV resonance line and dielectronic satellite intensities have been measured as functions of time for several flares recorded by the Naval Research Laboratory crystal spectrometer (SOLFLEX) flown on the US Air Force P78-I spacecraft. The intensity ratios of the Fe XXV resonance line, the Fe XXIV n = 2 satellite line j, and the Fe XXIV n = 3 satellite line d13 indicate that nonthermal electron energy distributions occur during the impulsive phase of the flares. For the electron energies at which the j and d13 satellites are formed (4.7 and 5.8 keV, respectively), the electron energy distributions during the impulsive phase are observed to have a bump or to be nearly flat. For all of the flares that were studied, hard X-ray bursts occurred near the time of the nonthermal distributions observed in the SOLFLEX data.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 319; 541-554
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  • 85
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    On 'Bimodality of the solar cycle' and the duration of cycle 21 (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Data from the well-observed cycles 8-20 are used to study the duration of cycle 21 and the bimodality of the solar cycle which is clearly seen in the scatter diagrams of descent versus ascent durations. A linear fit for long-period cycles suggests that cycle 21 will have a 141-month cycle duration. Like cycle 11, cycle 21 is found to occur on the downward envelope of the sunspot number curve, yet to be associated with an upward first difference in amplitude. Similarities between the two cycles suggest that cycle 21 may also have an extended tail of sustained, low smoothed sunspot number, with the cycle 22 minimum occurring either in late 1987 or early 1988.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 108; 1, 19; 195-200
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  • 86
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    Cosmic ray variations and magnetic field fluctuations in the outer heliosphere (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: It is formally confirmed that Galactic-cosmic-ray intensity variations measured by Voyager 2 during recovery from solar maximum are caused by traveling compressions and rarefactions in the mean interplanetary magnetic field. Voyager magnetic-field data are used as input to a time-independent, spherically symmetric, cosmic-ray-transport equation in the force-field approximation. The solutions closely followed the count rate of cosmic rays greater than 75 MeV/nucleon over 4 years, during the recovery phase of the 11-year solar-driven cosmic-ray cycle. This strongly supports prior theoretical assertions that turbulent interaction regions traveling with the solar wind are the major cause of the solar-cycle variation of Galactic cosmic rays in the ecliptic region.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 6127-613
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  • 87
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    The solar wind interaction with comets: A post encounter view (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The recent spacecraft encounters with comets Giacobini-Zinner and Halley have led to an enormous increase in our knowledge of comets, including their dust, neutral gas, plasma, and magnetic field environments. The latter has in turn led to better understanding of the nature of the solar wind interaction with the well developed atmosphere of a comet. The post-encounter understanding of this interaction is reviewed, underscoring the differences with pre-encounter reasoning. The problems outstanding in this area are emphasized.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 50
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  • 88
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    Solar wind effects on the outer ion coma of Comet Halley (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A simple two-dimensional model is developed to examine the composition of the cometary ion coma in the region outside the ionopause which is strongly affected by the solar wind. Two-dimensional ion distributions are obtained assuming a cylindrically symmetric ion coma which accounts for the dynamic effects of the mass-loaded solar wind flow around the cometary ionosphere. The results of this model are discussed in the context of analyzing the GIOTTO ion data.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 47
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  • 89
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    Solar wind-cometary interaction at the ionopause and associated phenomena (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Solar wind-cometary interaction at the cometary ionopause (including the tail) is reviewed in the context of recent missions to comets Giacobini-Zinner and Halley. The role of various MHD instabilities is discussed. The apparent marginal instability of the ionopause of the comet Giacobini-Zinner and the stability of the comet Halley (for large wavelength perturbations) are explained essentially in terms of the different solar wind conditions encountered by the two comets. Nonlinear evolution of the instability is discussed. Waves of large amplitude arising due to the instability may intermix the plasma and result in heating and particle acceleration. A number of the observed phenomena found a natural explanation in terms of this mechanism.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 45
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  • 90
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    Solar-terrestrial research in the space station era (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Because of the immense size of the solar-terrestrial system and its tightly-coupled physical nature, its study requires a carefully planned and coordinated approach using a variety of observational techniques. Of fundamental importance is the simultaneous measurement of the varying Sun, the solar wind, and the Earth's magnetosphere and atmosphere. These multiple measurements require a multi-spacecraft approach with both remote sensing of the Sun and atmosphere and in-situ measurements of the solar wind and magnetosphere. The decade of the 1990s will bring an opportunity to carry out the simultaneous set of measurements using a combination of instruments on missions such as the International Solar Terrestrial Physics Program, the GOES satellites, and the Space Station. For the first time it will be possible to determine solar variability and to sample the response of the solar wind and geospace portion of the environment in a thorough way. The potential opportunities for solar-terrestrial studies during the coming era of the Space Station are disclosed.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 44
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  • 91
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    Large-scale interaction of the solar wind with comets Halley and Giacobini-Zinner (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: In-situ measurements of comets Halley and Giacobini-Zinner have confirmed the accepted basic physics of comet/solar wind interaction. The solar wind magnetic field is captured by the comet through the mechanism of field-line loading by cometary ions and the field lines drape around the cometary ionosphere. With this basic model in hand, the large-scale structure of the plasma tail as revealed by submissions to the Large Scale Phenomena Network of the International Halley Watch is reviewed. The turn-on and turn-off of plasma activity seem consistent with theory. Some 16 obvious disconnection events (DEs) have been recorded. Preliminary results showed agreement with the sector-boundary model; a detailed analysis of all DEs will be required in order to make a definitive statement. A study of plasma activity around the time of the VEGA encounters provides strong support for the sector-boundary model and illustrates once again the power of simultaneous remote and in-situ measurements.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 41
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  • 92
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    Interaction of interplanetary shocks with nonuniform ambient solar wind (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Three interplanetary shock wave events are selected from the plasma and magnetic field data of Helios 1 and 2, IMP-8, and Voyagers 1 and 2 for study of the interactions of a weak interplantary shock with a nonuniform ambient solar wind. These events occurred during the periods 22-26 November 1977, 1-7 January 1978, and 2-5 April 1979, respectively. It is found that the shock surfaces of these events are highly distorted. In addition, a portion of the shock surface may be degenerated into a disturbance which does not satisfy the Rankine-Hugoniot jump conditions.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 35
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  • 93
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    A two-fluid model for solar wind fluid with higher order moments (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A spherically symmetric two-fluid model for the solar wind with higher-order moments is presented. In this model, continuity, momentum, temperature and heat flux equations for two components (electrons and protrons) in steady solar wind states are simultaneously solved by using a time-dependent method. This work is used to compare solutions of the steady-state solar wind with and without higher order moments, and to study the effects of thermal conduction. The coupling between electrons and protrons is also given special attention. The numerical solutions of the steady-state solar wind in both subsonic and supersonic regions between the Sun and 1 AU are obtained and graphically illustrated.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 34
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  • 94
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    The large Type 4 radio burst event of 24 April 1985 interpreted by dynamic spectral recordings and associated recordings (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Active Region 4647 showed a sudden increase in spot area on 23 April 1985 as well as an appearance of the D magneic configuration. During STIP interval XVII numerous subflares occurred in this region but only one very large event which exhibited all signatures of a classical p-event, well separated in time from other large events. The dynamic spectrum was observed at Bleien, Ondrejov, and Weissenau. The onset of radiation at m- and dm-waves is impulsive, and at dm-waves the preceeding dm continuum rises gradually. The absolute fluxes show very high readings of some 10 to the 4th power SFU at m-waves and some 5 x 10 to the 3d power at cm waves. High energy particles were observed about a day later by IMP 8. A Forbush decrease was seen on the neutron monitors but there was no GLE. The GOES X-ray flux monitors showed a gradual rise to high fluxes and a slow decrease over several hours. This information was extracted from Gdata but also from numerous letters from other observers and interpreters. More detailed data on the event and on the concomitant active region are to be presented.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 10
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  • 95
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    Solar energetic particles events observed by Prognoz-10 Intercosmos (May-October 1985) (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: On 26 April 1985, Intershock began observation of a solar energetic particle (SEP) event, resulting from a 3B solar flare which originated on 24 April. The following observation period was quiet with only a few weak increases of low-energy protons of several days duration. Two prominent SEP events occurred on 9 July 1985 (start 0133 UT, position S13, W25) and 17 July (no optical data, type II radio burst from 0333 to 0348 UT). These mass ejection and particle propagation episodes were studied on the basis of X-ray, radio, and energetic particle emissions.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 8
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    The largest white light flare ever observed: 25 April 1984, 0001 UT (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The X13/3B flare of 25 April 1984, 0001 UT, was accompanied by intense white light emission that reached a peak power output approx 2x10 to the 29 erg/sec in the optical/near UV continuum; the total energy radiated in the continuum alone reached 10 to the 32 power ergs. This was the most powerful white light flare yet recorded, exceeding the peak output of the largest previously known event by more than one order of magnitude. The flare was a two-ribbon type with intense embedded kernels as observed in both Balmer-alpha line and Balmer continuum, and each of these flare ribbons covered separate umbrae shortly after the maximum of the event. The onset and peak of the white light emission coincided with the onset and peak of the associated E greater than 100 KeV hard X-ray burst, while the 1-8 angstrom soft X-ray emission reached its maximum 4 minutes after the peak in white light.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 6
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  • 97
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    Low altitude flux and dose measurements during two solar flare events (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The dosimeter on board the low altitude polar orbiting DMSP/F7 satellite makes dose and flux measurements for electrons with energies greater than 1.0, 2.5, 5.0 and 10.0 MeV; and for protons with energies greater than 20, 35, 51, and 75 MeV. The characteristics and performance of the dosimeter are illustrated by presenting dose and flux data taken during the solar flare proton events of February 16 and April 26, 1984.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 5
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    Probable detection of solar neutrons by ground-level neutron monitors during STIP interval 16 (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The third solar neutron event detected by Earth-orbiting spacecraft was observed during STIP Interval XVI. The solar flare beginning at 2356 UT on 24 April l984 produced a variety of emissions including gamma rays and solar neutrons. The neutrons were observed by the SMM satellite and the neutron-decay protons were observed on the ISEE-3 spacecraft. Between 0000 and 0010 UT on 25 April an increase of 0.7 and 1.7 percent was recorded by neutron monitors at Tokyo (Itabashi) and Morioka, Japan. These stations were located about 42 degrees from the sub-solar point, and consequently, these is approximately 1400 grams of atmosphere between the incident neutrons at the top of the atmosphere and their detection on the Earth's surface. Nevertheless, the time coincidence of a small increase in the total counting rate of two independent neutron monitors indicates the presence of solar neutrons with energies greater than 400 MeV at the top of the Earth's atmosphere. The small increases in the counting rate emphasize the difficulty in identifying similar events using historical neutron monitor data.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 7
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  • 99
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    Overview of the MONSEE UAG report on STIP intervals No. 15 and 16: The 24-25 April 1984 Forbush decrease period (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The solar-terrestrial activity of 24-25 April 1894 is reviewed based on the MONSEE UAG-96 Report Solar-Geophysical Activity Reports for STIP Interval XVI 12-21 February 1984 Ground Level Event and STIP Interval XVI 20 April- 4 May 1984 Forbush Decrease (Helen E. Coffey and Joe H. Allen, compilers). A large 3B/X13.0 solar flare at 2356 UT on 24 April 1984 from the S11 E45 Solar Active Region (AR) 4474 produced major interplanetary and terrestrial environmental changes. The solar activity, the event itself, and the consequential, though temporary changes in the interplantary environment, in the near Earth space environment, and in the Earth's ionosphere and magnetic filed are discussed. For the Study of Travelling Interplanetary Phenomena (STIP) Symposium, emphasis will be placed on the solar, interplanetary, and cosmic ray observations.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 4
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  • 100
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    Overview of STIP intervals 15-19 (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Five STIP Intervals for special scientific study of solar and interplanetary phenomena were designated between February 1984 and March 1986. The first two intervals were selected retrospectively after unusual periods of solar activity; the remaining three intervals were selected in advance in conjunction with anticipated spacecraft configurations and measurements. In this overview the historical background of these STIP Intervals and a summary of the rationale in the selection of these particular time periods for concentrated studies are presented.
    Keywords: SOLAR PHYSICS
    Type: Alabama Univ., Huntsville. STIP Symposium on Physical Interpretation of Solar(Interplanetary and Cometary Intervals; p 2
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