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  • Other Sources  (279)
  • SOLAR PHYSICS  (279)
  • 1980-1984  (279)
  • 1950-1954
  • 1981  (279)
  • 1
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    Measurement of the solar constant (1981)
    In:  CASI
    Details
    Publication Date: 2006-06-04
    Description: The absolute value of the solar constant and the long term variations that exist in the absolute value of the solar constant were measured. The solar constant is the total irradiance of the Sun at a distance of one astronomical unit. An absolute radiometer removed from the effects of the atmosphere with its calibration tested in situ was used to measure the solar constant. The importance of an accurate knowledge of the solar constant is emphasized.
    Keywords: SOLAR PHYSICS
    Type: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
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  • 2
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    Solar spectrum from 170 to 3200 nanometers (1981)
    In:  CASI
    Details
    Publication Date: 2006-06-04
    Description: The spectral irradiance of the Sun between 170 and 3200 nanometers was measured to determine accurately the solar constant, its possible variation with the solar cycle, and the wavelength range responsible for the observed variations. It is pointed out that measurements over very long time periods (10 years) involving flights of the same instrument on future Spacelab missions will be required. Few spectral solar irradiation measurements ranging from the near ultraviolet to the near infrared have been performed yet. The most extensive solar irradiation measurements were obtained by a spectrometer onboard an aircraft or from high altitude observatories. The full disk irradiation flux was measured, corrections for atmospheric absorption are applied in all of the measurements.
    Keywords: SOLAR PHYSICS
    Type: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
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  • 3
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    Solar Maximum Mission Experiment - Ultraviolet Spectroscopy and Polarimetry on the Solar Maximum Mission (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacecraft is described. It is pointed out that the instrument, which operates in the wavelength range 1150-3600 A, has a spatial resolution of 2-3 arcsec and a spectral resolution of 0.02 A FWHM in second order. A Gregorian telescope, with a focal length of 1.8 m, feeds a 1 m Ebert-Fastie spectrometer. A polarimeter comprising rotating Mg F2 waveplates can be inserted behind the spectrometer entrance slit; it permits all four Stokes parameters to be determined. Among the observing modes are rasters, spectral scans, velocity measurements, and polarimetry. Examples of initial observations made since launch are presented.
    Keywords: SOLAR PHYSICS
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  • 4
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    High resolution X-ray spectra of solar flares. V - Interpretation of inner-shell transitions in Fe XX-Fe XXIII (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The paper examines high-resolution solar flare iron line spectra recorded between 1.82 and 1.97 A by a spectrometer flown by the Naval Research Laboratory on an Air Force spacecraft launched on 1979 February 24. The emission line spectrum is due to inner-shell transitions in the ions Fe XX-Fe XXV. Using theoretical spectra and calculations of line intensities obtained by methods discussed by Merts, Cowan, and Magee (1976), electron temperatures as a function of time for two large class X flares are derived. These temperatures are deduced from intensities of lines of Fe XXII, Fe XXIII, and Fe XXIV. The determination of the differential emission measure between about 12-million and 20-million K using these temperatures is considered. The possibility of determining electron densities in flare and tokamak plasmas using the inner-shell spectra of Fe XXI and Fe XX is discussed.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 245
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  • 5
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    Preliminary observations and results obtained with the ultraviolet spectrometer and polarimeter (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: New observation with the Ultraviolet Spectrometer and Polarimeter (UVSP) of a number of manifestations of solar activity obtained during the first three months of Solar Maximum Mission operations are presented. Attention is given to polarimetry in sunspots, oscillations above sunspots, density diagnostics of transition-zone plasmas in active regions, and the eruptive prominence - coronal transient link.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 6
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    The solar flare of 1980 March 29 at 0918 UT as observed with the hard X-ray burst spectrometer on the Solar Maximum Mission (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 7
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    On the polarization state of hydromagnetic fluctuations in the solar wind (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: From presently available observations one can infer that the Alfvenic turbulence measured in the solar wind, predominantly on trailing edges of high-speed streams, is a mixture of modes with two different polarizations, namely, Alfvenic modes and modes which are the incompressible limit of slow magnetosonic waves. Using Helios 2 magnetic data and a variance analysis, parallel (to the mean field) and perpendicular components of the fluctuations are separated, and the possible correlation between such components which would be predicted as a consequence of the incompressible character of the turbulence is studied. Correlations between eigenvalues of the variance matrix are also investigated and discussed.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 86; Mar. 1
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  • 8
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    Time and energy dependence of heavy ion abundances in solar flare energetic particle events (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Examples are presented of the time and energy dependence of the abundances and spectra of the major heavy ions He, C, O and Fe during solar flare events, taken from a survey using the UMD/MPI ULET telescope on IMP-8 during 1973-1977. In some cases, time variations were found in the O/He, O/C and Fe/O ratios which appear to be inconsistent with models based solely on rigidity dependent propagation in the interplanetary medium.
    Keywords: SOLAR PHYSICS
    Type: Contrib. to the 17th Intern. Conf. on Cosmic Rays; p 5-8
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  • 9
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    High-sensitivity circular polarimetry of the Sun, 0.5 - 1.7 microns (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Using an isometric (symmetrical) photoelastic-modulator polarimeter and a Cassegrain telescope, broadband polarization measures of the Sun were obtained with unprecedented sensitivity. With an instrumental background of x 10 to the minus 6th power differential effects delta q = V/I of 1 x 10 to the minus 7th power were detectable. Some results: (1) the lambda dependence of broadband circular polarization in spots was observed out to 1.7 mu, extending the visible-light measurements of Illing, Landman, and Mickey. The q drops to of the order of 1 x 10 to the minus 5 power at 1.2 mu (in a strong spot), then rises at 1.6 mu. While molecules or other special mechanisms must play a role in the visible-light polarization, at lambda 1.5 mu the q values seem consistent with gray magneto-opacity. (2) By surveying inactive regions upper limits are set to broadband polarization due to global or deep-seated magnetic fields. For a double-toroidal pattern a differential measure is found, q sub b = (q sub ne + q sub sw - q sub nw - q sub - se) 14, at 1.7 mu, of (+1.2 + or = 0.7) x 10 to the minus 7th power a mean from three series in 1981. Based on a simple estimate by L. Biermann this would correspond to deep-down toroidal fields of or approx 2000 gauss. Extension of this work are discussed.
    Keywords: SOLAR PHYSICS
    Type: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 191-197
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  • 10
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    Solar plages and the interpretation of stellar Ca 2 H and K line variations in late type dwarfs (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Approximately a dozen late type dwarf stars have been observed by Wilson (1978) to undergo cyclic variability in Ca II H and K line emission which seems analogous to the solar activity cycle. What might be learned about these stars from solar analogies? The Ca II K index is estimated variation of the Sun viewed as a star, and compared with the observed range of Wilson's stellar observations. Results indicate trends of increasing relative variation H-K(max)/H-K(min) with later spectral type, due to decreasing dilutional contribution of residual photospheric flux to a 1 A band at line center, and of increasing relative variation with decreasing relative time of rise to maximum tau rise/tau reminiscent of the observed solar correlation of a quick rise to sunspot maximum with a strong cycle.
    Keywords: SOLAR PHYSICS
    Type: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 181-189
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  • 11
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    Modification of average coronal properties in the presence of periodic temperature and density variations near the base (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Conductive damping of the transient motion of the solar corona, and the consequences on the average flow field of conductively re-distributed energy are discussed. A particular example is treated. First, a steady solution for solar wind flow is found for a given set of steady boundary conditions, between 1.4 and 28 solar radii. These boundary conditions are that the density is 1.6xEO6 cm-3 and the temperature is 1.6xEO6 degrees. The flow profiles for this initial state are those shown at t=0 in the figures. Then, at t=0, periodic, in phase, sinusoidal variations in temperature and density are initiated and continued indefinitely. The amplitudes of the variations are 5 percent and 7.5 percent for the temperature and density respectively, imposed at 1.4 solar radii. The variations have a period of 1 hour shorter than a coronal transit time, but sufficiently long for the disturbances to propagate for small distances (2 to 3 solar radii). These oscillations are like those that might occur for acoustic oscillations, although no explanation is offered as to how an acoustic oscillation might extend to this radius in the first place.
    Keywords: SOLAR PHYSICS
    Type: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 113-120
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  • 12
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    Dynamic phenomena in coronal flux tubes (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The study of stellar atmospheres and the determination of specific physical mechanisms, geometries, and magnetic structures by which coronae are maintained is examined. Ultraviolet and soft X-ray components observed in the radiative output of cool stars and the Sun require counterentropic temperature gradients for their explanation. The existence of a hot corona is recognized as a result of mechanical or fluid dynamic effects and the importance of the magnetic field in the heating is accepted. Magnetohydrodynamic energy release associated with the emergence of magnetic flux through the chromosphere and its dynamic readjustment in the corona are major counterentropic phenomena which are considered as primary candidates for corona heating. Systematic plows in coronal flux tubes result from asymmetric heating and systematic flows can exist without substantial chromospheric pressure differences.
    Keywords: SOLAR PHYSICS
    Type: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 53-58
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  • 13
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    Eruptive solar magnetic fields (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The quasi-steady evolution of solar magnetic fields in response to gradual photospheric changes is considered, with particular attention given to the threshold of a sudden eruption in the solar atmosphere. The formal model of an evolving, force-free field dependent on two Cartesian coordinates is extended to a field which is not force free but in static equilibrium with plasma pressure and gravity. The basic physics is illustrated through the evolution of a loop-shaped electric current sheet enclosing a potential bipolar field with footpoints rooted in the photosphere. A free-boundary problem is posed and then solved for the equilibrium configuration of the current sheet in a hydrostatically supported isothermal atmosphere. As the footpoints move apart to spread a constant photospheric magnetic flux over a larger region, the equilibria available extend the field to increasing heights.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 251
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  • 14
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    Radio evidence for shock acceleration of electrons in the solar corona (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is pointed out that the new class of kilometer-wavelength solar radio bursts observed with the ISEE-3 Radio Astronomy Experiment occurs at the reported times of type II events, which are indicative of a shock wave. An examination of records from the Culgoora Radio Observatory reveals that the associated type II bursts have fast drift elements emanating from them; that is, a herringbone structure is formed. It is proposed that this new class of bursts is a long-wavelength continuation of the herringbone structure, and it is thought probable that the electrons producing the radio emission are accelerated by shocks. These new events are referred to as shock-accelerated events, and their characteristics are discussed.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters; 8; Dec. 198
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  • 15
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    Solar wind motion within 30 R solar masses - Spacecraft radio scintillation observations (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: New remote-sensing observations are reported of the solar wind motion within about 30 earth radii. Use is made of the interplanetary scintillation (IPS) spaced receiver technique with the radio source being a spacecraft signal (rather than a natural radio source as in previous spaced receiver studies). The spacecraft used are Helios A and B and the Viking orbiters. The purposes of the study are (1) to augment the scarce estimates of solar wind bulk flow speed near the sun and in the ecliptic with measurements made using spacecraft signals, and (2) to estimate random velocity components and identify the region where the random velocity is a significant fraction of the mean velocity. In addition, the radial evolution of speed and random velocity is compared with that of the plasma density fluctuation spectrum. Also reported are the first accurately normalized IPS scintillation index measurements using a monochromatic point source.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 103; 2, No; Nov. 198
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  • 16
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    The structure and dynamics of the heliospheric current sheet (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It has been suggested that the sector structure observed in the interplanetary magnetic field may be interpreted in terms of a warped equatorial current sheet in the heliosphere. The reported study seeks to investigate this suggestion and to provide a clear picture of the topology of the current sheet. An analysis is presented of the magnetic field data obtained by the Pioneer 10 and 11 spacecraft during the time from 1972 to 1976, taking into account a range of heliocentric distances from 1 to 8.5 AU. The single most convincing observation in support of the warped current sheet hypothesis is the almost complete disappearance of the sector structure in the Pioneer 11 data when the spacecraft reaches a heliographic latitude of 16 deg in 1976. The observation suggests that the spacecraft was consistently above the current sheet for a period of several months.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 86; Dec. 1
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  • 17
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    The field and plasma configuration of a filament overlying a solar bipolar magnetic region (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: This paper presents an analytic model for a finite-size straight filament suspended horizontally in a steady state over a bipolar magnetic region. The equations of magnetostatic equilibrium are integrated exactly. The solution obtained illustrates the roles played by the electric current, magnetic field, pressure, and plasma weight in the balance of force everywhere in space. A specific example of a filament of diameter 50,000 km, with a density two orders of magnitude over the corona and supported by a magnetic field of about 4 gauss is included. The filament temperature can take values ranging from a small fraction to a few times the coronal temperature, depending on the internal electric current of the filament. To produce a cool filament, such as the quiescent prominence, the solution is required to have an internal field with a strong component along the filament, giving rise to helical structures. A hot filament such as the X-ray coronal loop can be produced as a twisted magnetic flux tube embedded in a strong background field aligned parallel to the filament and having lower density and temperature. The basic steps of construction can be used to develop models more realistic than the ones presented for their analytic simplicity.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 18
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    Bowen fluorescence on the sun (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An identification is made of a weak line in the high-resolution EUV solar spectrum, and the contribution of the Bowen fluorescence mechanism to line emission is considered. The line at 303.625 A is noted to coincide with the 2p 3d(3P2 0) - 2p2(3P1) transition of O III at 303.621 A, which could be excited by He II line excitation of the O III 2p2(3P2) - 2p 3d(3P2 0) transition at 303.799 A. Computations of the collisionally induced intensities of the 2p2(3P) - 2p3d(3P 0) multiplet are shown to result in values not observed in the solar spectrum, indicating that Bowen fluorescence, rather than collisional excitation, is the source of the line. The Bowen fluorescence mechanism is noted to have implications for the identification of other spectral lines, and for models of the solar corona.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 243
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  • 19
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    Latitude dependence of solar wind velocity observed at not less than 1 AU (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The large-scale solar wind velocity structure in the outer heliosphere has been systematically analyzed for Carrington rotations 1587-1541 (March 1972 to April 1976). Spacecraft data were taken from Imp 7/8 at earth, Pioneer 6, 8, and 9 near 1 AU, and Pioneer 10 and 11 between 1.6 and 5 AU. Using the constant radial velocity solar wind approximation to map all of the velocity data to its high coronal emission heliolongitude, the velocity structure observed at different spacecraft was examined for latitudinal dependence and compared with coronal structure in soft X-rays and H-alpha absorption features. The constant radial velocity approximation usually remains self-consistent in decreasing or constant velocity solar wind out to 5 AU, enabling us to separate radial from latitudinal propagation effects. Several examples of sharp nonmeridional stream boundaries in interplanetary space (about 5 deg latitude in width), often directly associated with features in coronal X-rays and H-alpha were found.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 86; Jan. 1
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  • 20
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    Dynamics of solar cosmic ray events - Processes at large heliocentric distances /much greater than 1 AU/ (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations of solar cosmic ray events at heliocentric distances up to 6 AU and beyond obtained by the Pioneer 10 and 11 spacecraft are discussed in terms of the propagation of energetic charged particles in interplanetary space. Following a review of the diffusion propagation model used to explain cosmic ray transport, the statistical studies of McCarthy and O'Gallagher (1976) and Zwickl and Webber (1977) of the relations of event parameters with radial distance and the simultaneous observation studies of Hamilton (1977) are reviewed, and it is noted that the results imply a slowly increasing radial diffusion coefficient out to about 6 AU. More recent analyses of data obtained at heliocentric distances greater than 10 AU are then presented which indicate that the coefficient of radial diffusion may actually be decreasing with radial distance beyond 5 AU. Finally, theoretical predictions of the radial variation of the diffusion coefficient are presented which take into account the background interplanetary medium and are shown to be in agreement with observations.
    Keywords: SOLAR PHYSICS
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  • 21
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    Photospheric subrotations, differential rotation and zonal wind bands - A reverse pirouette (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is noted that on the sun the core is assumed to be rotating with a period of about 12 days while the overlying 'mantle' convection zone has a solid body component of about 27 days. It is proposed that this phenomenon could simply be understood as a 'reverse pirouette'. It is noted that while previously proposed models provide solutions of valid equations and computer analyses, they lack a simple physical picture to explain the phenomenon. In the model proposed here, the solar oblateness is conventionally providing added heat input at the poles. The result is the large scale transport of material toward the equator, causing subrotation. The model is thus seen as facilitating an understanding of the formation of a slowly rotating convection zone above the more rapidly rotating core. The latitudinal photospheric differential rotation is interpreted as a 'second order' effect associated with the horizontal transport of momentum.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 71; May 1981
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  • 22
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    Fast plasma heating by anomalous and inertial resistivity effects in the solar atmosphere (1981)
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    Publication Date: 2011-08-18
    Description: A simple model is presented to describe fast plasma heating by anomalous and inertial resistivity effects. It is noted that a small fraction of the plasma contains strong currents that run parallel to the magnetic field and are driven by an exponentiating electric field. The anomalous character of the current dissipation derives from the excitation of electrostatic ion-cyclotron and/or ion-acoustic waves. The possible role of resistivity deriving from geometrical effects ('inertial resistivity') is also considered. Using a marginal stability analysis, equations for the average electron and ion temperatures are derived and numerically solved. No loss mechanisms are taken into account. The evolution of the plasma is described as a path in the drift velocity diagram, where the drift velocity is plotted as a function of the electron to ion temperature ratio.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 245
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  • 23
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    The corona associated with solar filaments (1981)
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    Publication Date: 2011-08-18
    Description: Spectroheliograms in high temperature ions such as Fe XV show the existence of both filaments that are brighter than the ambient corona and filaments that are darker than the ambient corona. The relationship of the filaments to photospheric magnetograms is described, and a possible physical mechanism to explain the differences is discussed.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 71; May 1981
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  • 24
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    Flares and dynamic aspects (1981)
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    Publication Date: 2011-08-18
    Description: Theory of the dynamic nature of solar flares, eruptive prominences, and coronal transients is surveyed. Two types of flare are considered: compact eruptions (small flares) which are probably loops, and large eruptions of double filament flares. The physical sense of this classification is justified, using solar observations. Even leaving the question unanswered of whether a coronal transient is a loop of ejected matter or a shock wave, the important, perhaps fundamental, role of mass motion in flare physics is evidenced.
    Keywords: SOLAR PHYSICS
    Type: Obs. de Paris-Meudon Forum on Solar Activity; 13 p
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  • 25
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    The coronal and interplanetary current sheet in early 1976 (1981)
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    Publication Date: 2011-08-18
    Description: A comparison of Helios 1 and 2 observations of the interplanetary sector pattern in early 1976 with the maximum brightness curves in the K coronameter data at 1.5 solar radii shows that the latter may be identified with the footprints of the sector boundary surface to an accuracy of about 10 deg. The sector boundary surface probably extended to about 15 deg in the Northern Hemisphere and to about 30 deg in the Southern Hemisphere, with little change between 1.5 solar radii and 1 AU. The surface was warped appreciably from a single titled plane (a dipole configuration) suggesting a significant magnetic quadrupole contribution.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 86; Oct. 1
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  • 26
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    On the theory of coronal heating mechanisms (1981)
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    Publication Date: 2011-08-18
    Description: The present state-of-the-art of two classes of theories of coronal heating is examined: (1) heating by acoustic processes in the 'nonmagnetic' parts of the atmosphere (the shock-wave theory is an example); and (2) heating by electrodynamic processes in the magnetic regions of the corona (beta much less than 1) either by MHD waves or current heating in regions with high electric current densities (flare-type heating). It is concluded that the mechanism of the heating of the solar chromosphere and corona remains an open question, especially in explaining detailed atmospheric structures. The acoustic theory might be correct with little modification for most of the chromosphere, but as soon as the atmosphere shows a high degree of structure as in the corona and transition layer the magnetic field must play a dominant role. It appears that the current heating theories have a small range of applicability, while the MHD-wave theories are the most promising.
    Keywords: SOLAR PHYSICS
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  • 27
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    Identification of new solar OH lines in the 10-12 micron region (1981)
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    Publication Date: 2011-08-18
    Description: High-resolution (0.02/cm) infrared solar spectra obtained with a balloon-borne interferometer reveal new solar absorption features, which appear as regularly spaced quartets, in the 825-960/cm region. The lines are interpreted as high N-double-prime (25-33) pure rotation lines of solar OH. An effective amount of approximately 8 x 10 to the 15th molecules/sq cm of OH is estimated from the spectra.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 248
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  • 28
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    On ionization equilibrium in solar flares as determined from X-ray emissionlines of Ca XVIII and Ca XIX (1981)
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    Publication Date: 2011-08-18
    Description: A diagnostic capable of determining the state of ionization equilibrium in flare plasmas is important for the determination of the physical conditions in flares. An experiment on the Air Force satellite P78-1 has provided high-resolution X-ray spectra which make it possible to determine the state of the ionization equilibrium in coronal flare plasmas. The considered investigation has the objective to show that the interpretation of the calcium results is complicated by several possible blends to line q, and to point out a variation in the observed ratios which seems difficult to account for. Possible explanations for the observations are discussed, taking into account the possibility that the ionization equilibrium calculations have to be improved. Another possible explanation is related to a suggestion made by Urnov (1981) and Karev et al. (1980) concerning the effects produced by the presence of high-energy nonthermal electrons.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 251
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  • 29
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    Solar observations and atomic data for the 3s2 1s0-3s3p 3P1 transition in S v (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: High resolution solar observations of the S v intersystem line at 1199.18 A are available from Skylab. This line is potentially useful as a density diagnostic for high density plasmas expected in solar flares. S v lines are also prominent in solar spectra at wavelengths below 1000 A. Collision strengths and radiative decay rates are calculated for levels of the configurations 3 s2, 3s3p, 3p2, and 3s3d. Level populations for the five lowest energy levels have been calculated as a function of electron density. These calculations are carried out assuming the temperature at which S v is most abundant in solar plasmas. The calculated population of the 3s3p 3P1 level reaches a pseudo-Boltzmann equilibrium at a density which is about five times higher than is derived from solar spectra and previous density determinations. It is believed that the discrepancy is due to a significant contribution from resonances to the 3s2-3s3p 3P excitation rate coefficient. It is suggested that the contribution of the resonances to the S v excitation rate coefficient can be estimated from a comparison of the experimental results and the theoretical calculations.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 250
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    Solar variability (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Reference is made to direct measurements carried out by space-borne detectors which have shown variations of the solar constant at the 0.2 percent level, with times scales ranging from days to tens of days. It is contended that these changes do not necessarily reflect variations in the solar luminosity and that, in general, direct measurements have not yet been able to establish (or exclude) solar luminosity changes with longer time scales. Indirect techniques, however, especially radius measurements,suggest that solar luminosity variations of up to approximately 0.7 percent have occurred within a period of tens to hundreds of years.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0185-1101)
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  • 31
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    Magnetic loop behind an interplanetary shock - Voyager, Helios, and IMP 8 observations (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The flow behind an interplanetary shock was analyzed through the use of magnetic field and plasma data from five spacecraft, with emphasis on the magnetic cloud identified by a characteristic variation of the latitude angle of the magnetic field. The size of the cloud was found to be about 0.5 AU in radial extent and greater than 30 deg in azimuthal extent, with its front boundary almost normal to the radial direction. Because the field direction of the magnetic cloud as it moved past the spacecraft was observed to rotate nearly parallel to a plane, it is thought that the field configuration of the cloud was essentially two-dimensional. These results further suggest that the lines of force in the magnetic cloud formed loops, but it could not be determined whether these loops were open or closed.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 86; Aug. 1
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  • 32
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    Coronal activity below 2 solar radii - 1980 February 15-17 (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Coronal observations concerning the area between the solar surface and 2.0 solar radii can now be conducted by making use of a new ground-based K-coronameter and a prominence monitor on Mauna Loa in Hawaii. Observations made by the K-coronameter on three consecutive days surrounding the eclipse of 1980 February 16 show that the solar corona was very active during this time. Definite changes occurred between each day's observations. During one period of K-coronameter observations (1980 February 15) a coronal transient was observed to move through the coronameter's field of view. A description is presented of the general changes which occurred in the corona during this period, taking into account the coronal transient observed by the prominence monitor and K-coronameter. The most important aspects of these new observations pertain to the relationship between the H alpha prominence and the surrounding coronal material.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 33
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    Determination of solar proton fluxes and energies at high solar latitudes by UV radiation measurements (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The latitudinal variation of the solar proton flux and energy causes a density increase at high solar latitudes of the neutral gas penetrating the heliosphere. Measurements of the neutral density by UV resonance radiation observations from interplanetary spacecraft thus permit deductions on the dependence of the solar proton flux on heliographic latitude. Using both the results of Mariner 10 measurements and of other off-ecliptic solar wind observations, the values of the solar proton fluxes and energies at polar heliographic latitudes are determined for several cases of interest. The Mariner 10 analysis, together with IPS results, indicate a significant decrease of the solar proton flux at polar latitudes.
    Keywords: SOLAR PHYSICS
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  • 34
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    What produces the high densities observed in solar flare plasmas (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Attention is drawn to the implications of the high densities observed in flare plasmas in the wide temperature range from 10 to the 4th K to more than 10 to the 7th K. The chromospheric evaporation theory for the decay phase is discussed, and it is found that it is not consistent with the observations. It is pointed out that all the flare mechanisms proposed so far, e.g., magnetic field reconnection in various geometries, have entirely ignored the fundamental problem of how the high densities arise in the first place, and, in fact, they are unable to answer this question. It is suggested that compressional heatings of a flaring loop might be responsible for the density and emission measure (EM) increases observed in flare plasmas. Chromospheric evaporation associated with local heating in the initial rising phase of the flare, in distinction to the existing evaporation theory which assumes a coronal heating source, is also discussed. Possible observational tests, utilizing the newly launched Solar Maximum Mission (SMM) satellite, are presented.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 97; 1, Ap; Apr. 198
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  • 35
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    Observations of solar flares on 1980 April 30 and June 7 with the hard X-ray burst spectrometer (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Descriptions of hard X-ray observations for solar flares occurring on 1980 April 30 and June 7 are presented. The hard X-ray light curve for the June 7 event shows complex intensity variations on time scales of 100 ms and spectral variations on time scales of seconds. The results for the 1980 April 30 flare are compared with simultaneous observations from other SMM instruments and from ground-based observatories. These comparisons have enhanced the interpretation of the hard X-ray data for this event and have permitted the tentative identification of the origin of the hard X-ray emission with a small loop structure within the flare region.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 36
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    Observations of the 1980 April 30 limb flare by the ultraviolet spectrometer and polarimeter on the Solar Maximum Mission (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations of the M2 limb flare of 1980 April 30 by the ultraviolet spectrometer and polarimeter in the C IV 1548 A line are described and compared with observations from other SMM instruments and with ground-based H-alpha data. Events observed during the 18 minutes leading up to the flare impulsive phase include the filling of a small loop with material moving at about 20 km/s, followed by a rapid brightening in C IV, H-alpha, and hard X-rays, with a subsequent brightening of a higher set of loops. The rapid brightening appears to be at the junction of the small loop with the overlying magnetic structures, which suggests the flare may be caused by their interaction.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 37
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    Some 20.7- and 31.4-GHz solar disk temperature measurements (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The performance of a 20.7/31.4 GHz water vapor radiometer was evaluated with respect to its use in measuring atmospheric noise temperature. Results are in good agreement with the results previously reported at the same frequency.
    Keywords: SOLAR PHYSICS
    Type: Telecommun. and Data Acquisition Progr. Rept. 42-64; p 140-159
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  • 38
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    Evolution of the energetic particle composition during solar flare events as observed by Voyager 1 and 2 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Measurements of the composition and energy spectra of the energetic ions from two solar flare particle events are presented. Their evolution with time during each event is discussed. The data are from the Low Energy Particle Telescope (LEPT) on Voyager 2, which can identify the major ion species (Z = 1-26) over an energy range of approximately 0.5-50 MeV/nucleon.
    Keywords: SOLAR PHYSICS
    Type: Contrib. to the 17th Intern. Conf. on Cosmic Rays; p 14
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  • 39
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    Observations of interplanetary energetic charged particles from gamma-ray line solar flares (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations of interplanetary energetic ions from the 7 June, 21 June and 1 July 1980 gamma ray line solar flares are presented. The observations are from the Max-Planck-Institut/University of Maryland Ultra Low Energy Wide Angle Telescope aboard the ISEE-3 spacecraft. Both June flares produced relatively low intensity proton events at earth with peak intensities at 10-20 MeV approximately 5 x .01 protons square cm sec sr MeV)-1. Neither flare showed evidence of being enriched in either 3He or Fe at approximately 1 MeV/nucleon. The 1 July flare produced no observable ion or electron enhancements.
    Keywords: SOLAR PHYSICS
    Type: Contrib. to the 17th Intern. Conf. on Cosmic Rays; p 1-4
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  • 40
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    A satellite investigation of energy flux and inferred potential drop in auroral electron energy spectra (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Because predicted relationship (epsilon directly varies with V squared) between auroral electron energy flux (epsilon) and the inferred acceleration potential drop (V) for accelerated Maxwellian distributions was favorably tested by other using sounding rocket data for the limiting case of eVE 1 (where Ec is the characteristic energy of the accelerated Maxwellian distribution) and for a single inverted-V observed by the Injun 5 satellite, data from Atmosphere D were used to extend these studies over the range .2 eV/Ec 5 and for a wide range of latitudes and local times on both the nightside and the dayside. Results show good agreement with the full accelerated Maxwellian model. An analytical approximation to the electron energy flux was derived which better describes the data over the range .2 eV/Ec approximated 3. Analyses of individual energy spectra at small and large pitch angles through well-defined inverted-V structures suggest that the altitude of the inferred potential drop maximizes near the center of the inverted-V's.
    Keywords: SOLAR PHYSICS
    Type: Texas Univ. at San Antonio Res. on Solar-Wind Magnetospheric Elec. Fields and Plasmas; 16 p
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  • 41
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    On the anticorrelation between the He-3/He-4 ratio and proton intensity in He-3 rich flares (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A model is presented which can explain the observed anticorrelation between the size of the 3He/4He abundance ratio at greater than or approximately 10 MeV/nuc and the peak intensity of approximately 10 MeV protons in 3He rich events. If 3He is preaccelerated with respect to 4He prior to the main ion acceleration phase, and if the main ion acceleration phase has an effective injection cutoff which varies from flare to flare, the observed anticorrelation follows naturally.
    Keywords: SOLAR PHYSICS
    Type: Contrib. to the 17th Inter. Conf. on Cosmic Rays; p 15-18
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  • 42
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    The Schwarzschild criterion for convection in the presence of a magnetic field (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Schwarzschild criterion governing the onset of convective instability has been modified to include magnetic field. This may be of importance for solar variability. The revised condition suggests that the underside of field layers are stabilizing and the upper side destabilizing. Absolute instability can be reached to achieve conventional magnetic buoyancy. This may explain the inverse correlation between the time intervals between sunspot minima and sunspot maxima with the maximum values of sunspot number, which is found to be significant at the 5.5 sigma level.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Letters; 21; 3-4,; 1981
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  • 43
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    Spatial and temporal structures of impulsive bursts from solar flares observed in UV and hard X-rays (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: New observations are presented of impulsive UV and hard X-rays bursts in two solar flares obtained with instruments on Solar Maximum Mission. The UV bursts were observed in the Si IV and O IV emission lines, whose intensity ratio is density-sensitive. By comparing the spatially resolved Si IV/O IV observations with the corresponding hard X-ray observations, it is possible to study their spatial and temporal relationships. For one flare, the individual component spikes in the multiply peaked hard X-ray burst can be identified with different discrete Si IV/O IV flaring kernels of size 4 arcsec x 4 arcsec or smaller, which brighten up sequentially in time. For the other, many Si IV/O kernels, widely distributed over a large area, show impulsive bursts at the same time, which correlate with the main peak of the impulsive hard X-ray burst. The density of the flaring Si IV/O IV kernels is in the range from 5 x 10 to the 12th-13th/cu cm.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 248
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  • 44
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    Simple-loop flares - Magnetic instabilities (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The era of rocket and spacecraft observations of the sun has provided an entirely new view of the structure and evolution of the solar atmosphere. It is now clear, particularly since the extended series of Skylab flights, that the lower corona is quite nonuniform. In active regions, the strong ambient magnetic fields collimate and confine the emissive plasma into a myriad of loops and arcades. These features are observed to evolve slowly, with a time-scale much longer than the relevant hydromagnetic of Alfven period and, therefore, must be considered generally to be stable. A conspicuous exception is the sporadic flare activity of these loops, which is believed to be due to localized departures from infinite-conductivity behavior.
    Keywords: SOLAR PHYSICS
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  • 45
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    Sunspot dynamics - Gravitational draining - A cooling mechanism (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The inward and downward flow of cooled material below sunspots is considered as a possible explanation of the stability, temperature and heat flow characteristics of sunspots. It is suggested that the flow of material inwards towards the center of the sunspot and then downwards towards the center of the sun through magnetic field conduits plays a role in the cooling of sunspots as it does in pores and magnetic knots, although due to the larger size of a sunspot the downflow takes place below the photosphere. In this view, the inflow and cooling of sunspots are sustained by the release of energy by the convecting gas, which then becomes cooler and denser as it returns to the heat source. The lack of a bright ring around sunspots is explained by the entrainment of upward moving heat flux by the downward moving gases. The temperature and density distributions predicted by the present model are shown to be satisfactory agreement with the empirical model of Van't Veer (Tandberg-Hansen, 1966).
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 247
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  • 46
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    A mechanism for solar ultraviolet flux variability (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Following an examination of solar UV emission observed by a filter photometer on Nimbus IV from 1969 to 1973 in an attempt to understand the 27-day and secular variability, two models are proposed to account for the variations: (1) a calcium plage model and (2) a chromospheric network faculae and spicule structure model. An association between UV brightenings and the large scale magnetic field has been found to be consistent with the network model. An increase in the UV emittance can be achieved by raising the effective chromospheric temperature closer to a photospheric level. If the sun's luminosity is constant on these time intervals, the enhanced UV radiation could be partially offset by an overall decrease in photospheric temperature such as that measured by Livingston (1978) in visible photospheric profiles.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 73; Sept
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  • 47
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    On the presence of electric currents in the solar atmosphere. I - A theoretical framework (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The general magnetic field above the solar photosphere is divided by an elementary analysis based on Ampere's law into two parts: a potential field due to electric currents below the photosphere and a field produced by electric currents above the photosphere combined with the induced mirror currents. The latter, by symmetry, has a set of field lines lying in the plane taken to be the photosphere which may be constructed from given vector magnetograph measurements. These field lines also represent all the information on the electric currents above the photosphere that a magnetograph can provide. Theoretical illustrations are given, and implications for data analysis are discussed.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 73; Oct. 198
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  • 48
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    Temperature anisotropy instabilities driven by Whang's ion model (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The behavior of four temperature anisotropy instabilities in a single-component space plasma is investigated theoretically using the solar wind model (i.e., heat flux modified non-Maxwellian velocity distribution functions) proposed by Whang (1972). The linear dispersion properties are studied in an infinite Vlasov plasma where the proton distribution is assumed to consist of one warm slow-speed component and where the electron background is isotropic. It is shown that the fire hose, mirror, and Harris instability do not occur under these conditions, and that only the ion cyclotron instability is of importance in Whang's ion model. Growth rates are shown to have values between 0.021 and 0.00011. Increasing temperature anisotropy causes the range frequencies where wave particle interaction occurs to be shifted toward the ion gyrofrequency.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 86; Sept. 1
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  • 49
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    Effects of changes in convective efficiency on the solar radius and luminosity (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A sequence of solar models has been constructed in order to investigate the sensitivity of the solar radius and luminosity to small changes in the ratio alpha of the mixing length lambda to the pressure-scale height Hp throughout the solar convective envelope. The basic procedure for determining this sensitivity was to impose a perturbation in alpha within the convective envelope and then to follow the resulting changes in the solar radius delta R and luminosity delta L for the next 10 to the 6th power yrs. These calculations gave the following results. (1) A perturbation in alpha produces immediate changes in the solar radius and luminosity. Initially delta L and delta alpha are related by delta L/L = 0.30 delta alpha/alpha. (2) The value of the ratio w = delta log R/delta log L is strongly time dependent. Its value just after the perturbation in alpha is 6.5 x 10 to the minus 4th power. (3) The ratio H = (delta log L) d delta log R/dt is much less time dependent and is a more suitable means for relating the changes in the solar radius and luminosity. (4) Both of these ratios imply that for any reasonable change in the solar luminosity the corresponding change in the solar radius is negligible.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 143-164
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  • 50
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    Variation of the Solar He I 10830 A Line: 1977 - 1980 (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Daily measurements of the equivalent width of the 10830 A He I line integrated over the visible disk show: (1) an increase from about 32 to about 74 mA in the monthly mean values from the minimum to the maximum of the current solar cycle; (2) the monthly mean values are more smoothly varying than most other indices of solar activity; (3) rotation modulates the daily values in a highly variable manner with amplitudes as large as plus or minus 20%; (4) the apparent synodic rotation period is 29 days rather than the expected 27 days associated with active regions; (5) despite great differences in the appearance of the sun in 3933 A Ca I and 10830 A He I, the central intensity of the former correlates with the equivalent width of the latter with a value r = 0.97.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 265-272
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  • 51
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    Sclera solar diameter observations (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Focus is given to possible variations in solar luminosity and accurate methods of monitoring it. Aside from direct bolometry, one methodology for this type of research makes use of measurements of the solar diameter and limb darkening function as indirect indicators of the solar luminosity. This approach was reviewed.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 123-128
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  • 52
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    The combined solar and tidal influence in climate (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: To provide an early warning indication of the CO2 warning signal, we are searching for periodic or projectable trends in climate. The strong 20.5 year oscillation in Eastern North American January temperature found by Mock and Hibler shows evidence of a beat between waves with periods of 22.36 (22.21 to 22.55) years and 18.64 (18.45 to 18.79) years with an opposition at about 1880. These are interpreted to be the 22.279 year solar Hale magnetic cycle and the 18.61 year lunar nodal tidal cycle. The lunar nodal cycle is known to produce changes in the sea surface temperature through increased mixing of the mixed layer of the ocean. This beat note is shown to be evident in the Western High Plains drought record of Mitchell, Stockton and Meko and to provide a better bit to the drought series, especially at the beat oppositions in 1880 and 1770.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 241-255
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  • 53
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    On the seat of the solar cycle (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A discussion of some of the issues raised in connection with the seat of the solar cycle are presented. Is the cycle controlled by a strictly periodic oscillator that operates in the core, or is it a turbulent dynamo confined to the convection zone and possibly a thin boundary layer beneath it? Sunspot statistics are discussed, with a view to ascertaining the length of the memory of the cycle, without drawing a definitive conclusion. Also discussed are some of the processes that might bring about variations delta L and delta R in the luminosity and the radius of the photosphere. It appears that the ratio W = delta lnR/delta lnL increases with the depth of the disturbance that produces the variations, so that imminent observations might determine whether or not the principal dynamical processes are confined to only the outer layers of the Sun.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 185-206
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  • 54
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    Solar radius measurements (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Preliminary results of measurements made during 1979-1980 are discussed. Variability in the radius measurements of 0.4 pi is found, of unknown origin.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 129-130
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  • 55
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    A general method for computing the total solar radiation force on complex spacecraft structures (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The method circumvents many of the existing difficulties in computational logic presently encountered in the direct analytical or numerical evaluation of the appropriate surface integral. It may be applied to complex spacecraft structures for computing the total force arising from either specular or diffuse reflection or even from non-Lambertian reflection and re-radiation.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Sixth Ann. Flight Mech.(Estimation Theory Symp.; 12 p
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  • 56
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    Predominant periods in the time series of drought area index for the Western High Plains AD 1700 to 1962 (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The detection of the combined presence of the Hale magnetic sunspot cycle (22.28 years) and the lunar nodal tidal cycle (18.61 years) in both the Eastern North American January air temperatures and the Western U.S. High Plains drought series led to an extended analysis of the Drought Area Index time series. This analysis indicated that the mean dominant period of the drought series should be 20.0 to 20.5 years and that the principal period should be resolvable into two components of about 22.28 and 18.61 years. This note details the successful accomplishment of this task.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 257-264
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  • 57
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    Solar pulsations and long-term solar variability (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The seismology of the solar atmosphere is important in relating changes in luminosity to variations in other observables. This approach has already led to the identification of properties which were not previously observed or recognized. Equally important results from solar seismology are expected in the future.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 229-233
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  • 58
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    An instrument to measure the solar spectrum from 170 to 3200 nm on board Spacelab (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: This instrument, at the present time in development, will fly on board Spacelab I in May 1983. Other flights are foreseen during the following missions. The instrument is composed of three double monochromators covering the range 170 to 3200 nm. The spectrometers have bandpasses of 1 nm up to 900 nm and 20 nm from 850 to 3200 nm with an accuracy 1/100 nm. Calibration lamps are included in the instrument to monitor any change of its sensitivity and wavelength scale.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 165-173
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  • 59
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    Estimating short-term solar variations by a simple envelope matching technique (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A simple matching technique is explained which allows the computation of the response of the solar surface to perturbations which occur at any depth within the convective envelope of the Sun. This technique was applied to a perturbation of the convective efficiency (alpha-mechanism), and of the non-gas component of the pressure (beta-mechanism) in different regions of the convection zone. The results indicate that either perturbation affects the solar luminosity. However, the alpha-mechanism has little effect in the solar radius, regardless of the location of the perturbed region, whereas the beta-mechanism produces radius changes that become quite large if the location of the perturbed region is deep within the solar convection zone.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 131-136
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  • 60
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    Observed variability in the Fraunhofer line spectrum of solar flux, 1975 - 1980 (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Over the five years double-pass spectrometer observations of the Sun-as-a-star revealed significant changes in line intensities. The photospheric component weakened linearly with time 0 to 2.3%. From a lack of correlation between these line weakenings and solar activity indicators like sunspots and plage, a global variation of surface properties is inferred. Model-atmosphere analysis suggests a slight reduction in the lower-photospheric temperature gradient corresponding to a 15% increase in the mixing length within the granulation layer. Chromospheric lines such as Ca II H and K, Ca II 8543 and the CN band head weaken synchronously with solar activity. Thus, the behavior of photospheric and chromospheric lines is markedly different, with the possibility of secular change for the former.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 95-109
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  • 61
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    The variability of the solar output (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A review of solar constant determinations and measurements of its spectral distribution is presented. For the period from 1966 to 1980 a mean value of 1367 Wm-2 was determined. Within the corresponding uncertainty, no significant change of both the integral value and the spectral distribution can be detected. However, short term solar variations and their spectral dependence were deduced from measurements during four hours on June 20, 1980 from 34 km altitude with amplitudes of + or - 500 ppm at 368 nm, of 200 ppm at 500 nm and + or - 150 ppm at 778 nm. Comparison with simultaneous total irradiance data of the Solar Maximum Mission (SMM) shows a high correlation which indicates the solar origin. The power spectrum shows a weak peak at about 3.2 mHz, which corresponds to the frequency of the 5 minutes solar oscillation.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 37-44
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  • 62
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    Monitoring solar-type stars (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Old UBV and recent uvby photometry of solar-type dwarfs and other standard stars yield an upper limit of variability (determined by observational errors) of about 0.004 mag rms. A factor two improvement in this upper limit is achievable.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 219-227
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  • 63
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    The horizontal and vertical semi-diameters of the Sun observed at the Cape of Good Hope (1834 - 1887) and Paris (1837 - 1906): A report on work in progress (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Cape and Paris meridian observations of the solar limbs which permit an estimate to be made of the solar semi-diameter were surveyed, sampled, and compared with Greenwich and U.S. Naval Observatory observations. Significant systematic errors were found in the Paris work and have been correlated with changes of instruments and observers. Results from the Cape series indicate that work should continue on the compilation of data from Cape observations of the Sun.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 111-116
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  • 64
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    Solar variability indications from Nimbus 7 satellite data (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The cavity pyrheliometer sensor of the Nimbus 7 Earth Radiation Experiment indicated low-level variability of the total solar irradiance. The variability appears to be inversely correlated with common solar activity indicators in an event sense. the limitations of the measuring system and available data sets are described.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard space Flight Center Variations of the Solar Constant; p 59-72
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  • 65
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    Review of ground-based measurements (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Early measurements of the solar constant are described and discussed with particular emphasis on the Smithsonian program. A brief description is given of the monitoring program currently operating at San Diego State.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 11-30
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  • 66
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    Observations of large-scale motions of the Sun (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Recent observations of large-scale mass motions on the Sun are discussed. The principal large-scale velocity flows are convection, rotation, meridional flow, and torsional and radial oscillations.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 235-240
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  • 67
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    Short and long term variations in the solar constant (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Short and long term variations in the solar constant are examined theoretically. The variations observed by the Solar Maximum Mission, lasting several days and associated with the passage of sunspot groups, strikingly demonstrates the well known lack of a bright ring effect around sunspots. This suggests that sunspot magnetic fields do not simply block the heat flowing upward into the photosphere. Rather, it is suggested that gravitational draining occurs; this cools sunspots and transports downward the heat that would otherwise flow into the photosphere. A model of sunspot temperature with depth shows modest support when compared with the empirical model of Van't Veer. Secular trends in the solar constant may occur and be associated with the influence of the convection zone magnetic field upon convective heat transport. As a start to understanding this problem, the Schwarzschild criterion has been modified to include the effects of magnetic field.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 207-217
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  • 68
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    A summary of results from solar monitoring rocket flights (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Three rocket flights to measure the solar constant and provide calibration data for sensors aboard Nimbus 6, 7, and Solar Maximum Mission (SMM) spacecraft were accomplished. The values obtained by the rocket instruments for the solar constant in SI units are: 1367 w/sq m on 29 June 1976; 1372 w/sq m on 16 November 1978; and 1374 w/sq m on 22 May 1980. The uncertainty of the rocket measurements is + or - 0.5%. The values obtained by the Hickey-Frieden sensor on Nimbus 7 during the second and third flights was 1376 w/sq m. The value obtained by the Active Cavity Radiometer Model IV (ACR IV) on SMM during the flight was 1368 w/sq m.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 45-58
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  • 69
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    Sensitivity of the Earth's climate to changes (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Climate modeling is discussed with emphasis on the control of major parameters in such modeling. Possible feedbacks which operate on long time scales and are therefore not testable directly, are also discussed. Examples of simplified models are presented. The accuracy of several models is assessed and suggestions for improvements for climatic modeling are given.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 1-10
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  • 70
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    Indirect methods for measuring variations of the solar constant (1981)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The difference between the methods that measure delta S, and those that measure variations in the solar luminosity, delta L, is discussed. It is shown that the past practice of simply relating delta S to delta L by geometrical arguments is not valid because of anisotropy of the solar radiation. It is concluded that direct techniques prove the existence of short term variability that is fully explainable in terms of the passage of active regions (spots and faculae) on the face of the Sun. The obervations of changes in the solar diameter support the existence of structurally induced variations of the solar luminosity on timescales of tens of years, which are significant in the understanding of climatic variations.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 73-79
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  • 71
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    Generation of coronal electric currents due to convective motions on the photosphere (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Generation of electric currents in a magnetized plasma overlying a dense convective layer is studied, assuming that the magnetic field perturbation is small and satisfies the force-free equation. Currents are produced by rotational motions on the boundary in the case of a uniform equilibrium field. In a simple two-dimensional bipolar configuration, however, both irrotational and incompressible motions give rise to currents, and the current density has a peak at the magnetic neutral line. Scaling laws for the current density as well as for the stored magnetic energy are derived, and the possibility of heating the solar corona through the dissipation of coronal currents generated in this way is discussed.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 248
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  • 72
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    The aluminum I autoionization doublet in the quiet solar spectrum (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations are presented of the Al I autoionization doublet 1932 A and 1936 A in the quiet solar spectrum, obtained from the NRL slit spectrograph aboard Skylab and from the University of Hawaii Echelle Rocket Spectrograph. The observed profiles are compared with theoretical spectra computed for the Harvard Smithsonian Reference Atmosphere and the Vernazza, Avrett and Loeser (1976) solar models. It is found that nonlocal thermodynamic equilibrium effects are important in the line-formation problem and the synthetic spectra are in good agreeement with the data.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 248
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  • 73
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    Detection of stopped solar flare helium in lunar rock 68815 (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Steep increases were detected in the concentration profiles of He-3 and possibly of Ne-21 in the near-surface layers of lunar rock 68815, which was exposed on the lunar surface for 2 Myr. The concentration profile of He-3 is inconsistent with either spallation or solar wind components, but it agrees with expected ranges of stopped solar flare particles. Although the He-3 retention in this rock is determined to be very low (approximately 3% at the surface), a long-term average solar flare ratio He-4/He-3 can be estimated at 12 to within a factor of about 3. This ratio is two orders of magnitude smaller than the same ratio observed in the solar wind, but it is consistent with solar flare data from recent satellite observations.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 247
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  • 74
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    Solar flare acceleration of solar wind - Influence of active region magnetic field (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The direction of the photospheric magnetic field at the site of a solar flare is a good predictor of whether the flare will accelerate solar wind plasma. If the field has a southward component, high-speed solar wind plasma is usually observed near the earth about 4 days later. If the field has a northward component, such high-speed solar wind is almost never observed. Southward-field flares may then be expected to have much larger terrestrial effects than northward flares.
    Keywords: SOLAR PHYSICS
    Type: AD-A104456 , Science; 212; June 26
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  • 75
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    Numerical study of solar flare particle propagation in the heliosphere (1981)
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    Publication Date: 2019-06-28
    Description: Numerical solutions are presented for the propagation of solar cosmic rays in interplanetary space, including the effects of pitch-angle scattering and adiabatic focusing. The intensity-time profiles can be well fitted by a simple radial spatial diffusion equation. For low-rigidity particles the radial mean free path so obtained is significantly larger than the mean free path calculated from the scattering coefficient due to the inapplicability of the diffusive approximation early in the event. The well-known discrepancy between the scattering mean free path and the theoretical predictions may be resolved by these calculations.
    Keywords: SOLAR PHYSICS
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  • 76
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    Direct observation of charge state abundances of energetic He, C, O, and Fe emitted in solar flares (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The ionic charge states of helium, carbon, oxygen, and iron have been determined for three solar particle enhancements by an electrostatic deflection analyzer, which is combined with a thin window proportional counter dE/dX vs. E system. The observations are obtained during the periods September 23 to 29, 1978, June 6 to 8, 1979, and September 15 to 26, 1979, with an instrument onboard the ISEE-3 spacecraft. The mean ionic charge states for He, C, and oxygen exhibit a high degree of ionization with values of Q equals 2, 6, and 7.2, respectively. The charge state of iron is near 13 charge units. Variations from flare to flare and within the September 23, 1978 flare are small. The most surprising feature of the charge state measurement is the observation of a small (about 10%) but finite contribution of singly ionized helium.
    Keywords: SOLAR PHYSICS
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  • 77
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    On compositional variations of heavy ions during solar particle events (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Intensity-time profiles of protons, alpha particles, and heavy ions (C, O, Fe) in the MeV/nucleon energy range have been analyzed for one solar particle event following the solar flare on September 23, 1978. The data have been obtained with the wide angle double dE/dx-E sensor of the Max-Planck-Institut/University of Maryland experiment onboard ISEE-3. Time variations in the iron to helium ratio of up to 2 orders of magnitude and a significant variation of the O/He ratio during this event have been found, whereas the C/O-ratio at the same energy/nucleon appears to be time independent. The influence of a rigidity dependent mean free path in interplanetary space and of rigidity dependent coronal propagation on heavy ion ratios during solar particle events was investigated.
    Keywords: SOLAR PHYSICS
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  • 78
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    Discrepancies between theoretical and empirical models of the flaring solar chromosphere and their possible resolution (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Possible sources of pronounced discrepancy between empirical and theoretical models of the solar chromosphere during flares are discussed. It is noted that a principal source of uncertainty in empirical models is the inhomogeneity of the spectral data on which they are based. With theoretical models, probably the most important source of error is neglect of the radiative coupling of upper and lower chromospheric regions. A new procedure for studying flare energy input is suggested wherein the required input is derived from the empirical model chromosphere. This procedure is applied to the electron-heated case, and it is found that the integral equation defining the flare energy deposition rate can be inverted analytically to yield the injected electron flux energy spectrum from knowledge of the energy balance in the empirical atmosphere. Recent empirical model results are analyzed in this manner, and the calculated injected electron flux spectrum is compared with that needed for hard X-ray bursts in moderately large flares.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 79
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    Magnetohydrodynamic interaction of high-speed streams (1981)
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    Publication Date: 2019-06-28
    Description: Numerical solutions of a magnetohydrodynamic model are carried out to describe the nonlinear interaction of corotating high-speed streams near the solar equatorial plane. Two problems are studied. The first problem is to simulate the evolution of an idealized high-speed stream. Numerical solutions are obtained to represent the variations of flow velocity, magnetic field, plasma density, temperature, and conduction heat flux in the interaction region. They demonstrate that the dynamical interaction and heat conduction process are responsible for the thermal structure of a high-speed stream. The second problem deals with the formation of corotating shock waves near the leading edge of a broad stream resulting from the merging of characteristic curves. Corotating shocks do not necessarily occur in pairs; a reverse shock can be formed without a forward shock nearby.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 86; May 1
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  • 80
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    Coronal heating by stochastic magnetic pumping (1981)
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    Publication Date: 2019-06-28
    Description: Recent observational data cast serious doubt on the widely held view that the sun's corona is heated by traveling waves (acoustic or magnetohydrodynamic). It is here proposed that the energy responsible for heating the corona is derived from the free energy of the coronal magnetic field derived from motion of the 'feet' of magnetic field lines in the photosphere. Stochastic motion of the feet of magnetic field lines leads, on the average, to a linear increase of magnetic free energy with time. This rate of energy input is calculated for a simple model of a single thin flux tube. The model appears to agree well with observational data if the magnetic flux originates in small regions of high magnetic field strength as proposed by Tarbell et al. (1979). On combining this energy input with estimates of energy loss by radiation and of energy redistribution by thermal conduction, scaling laws are obtained for density and temperature in terms of length and coronal magnetic field strength.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 81
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    Latitudinal anisotropy of the solar far ultraviolet flux - Effect on the Lyman alpha sky background (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An estimate is given for the anisotropy of the solar full disk flux in the far ultraviolet, as it would be observed for lines of sight within and above the ecliptic plane through the predominant influence of plages at low heliocentric latitudes. The flux anisotropy for Lyman alpha, at a level of solar activity with a sunspot number of roughly 160, is approximately 0.88 for the integrated flux over the Lyman alpha profile and 0.83 for the flux at line center. The effect of this Lyman alpha flux anisotropy on the Lyman alpha sky background intensity, resonantly backscattered from the local interstellar medium that is streaming through the solar system, is examined. It is concluded that the solar Lyman alpha anisotropy should be included in models of the interplanetary background during periods of moderate to high solar activity.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 97; 2, Ap; Apr. 198
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  • 82
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    Fourier Transform Spectrometer observations of solar carbon monoxide. I - The fundamental and first overtone bands in the quiet sun (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Measurements of the 2200/cm fundamental and 4300/cm first overtone vibration-rotation band systems of solar carbon monoxide, were obtained with the Fourier Transform Spectrometer of the McMath telescope at Kitt Peak. The overtone measurements were taken at the east, north, and west heliocentric limbs, and at disk center. Observations of the strong fundamental bands were obtained at disk center and near the north limb. The low core brightness temperatures of the strongest fundamental carbon monoxide lines near the limb, reported previously by Noyes (1972) and Hall (1974), are confirmed. The possibility that thermal inhomogeneities might be responsible for the unusual behavior of the fundamental carbon dioxide lines have been examined. The somewhat discordant behavior of the fundamental lines at disk center compared with the north limb seems to favor a limb shadowing effect. The first overtone limb equivalent widths and the best-fit thermal and microvelocity models indicate a solar carbon abundance of 0.004 (on the scale with A sub H = 1) for an oxygen-to-carbon abundance ratio of 2.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 245
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  • 83
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    An acceleration mechanism for loop transients in the outer corona (1981)
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    Publication Date: 2019-06-28
    Description: The heliocentrifugal motion of coronal loop transients is likely driven largely by the buoyant force exerted by the ambient medium. In the outer corona where the solar wind is well formed, the buoyant force results mainly from the rapid outward decrease in the ambient pressure of the solar wind. The contribution from magnetic buoyancy is not so significant as in the vicinity of the solar surface. Therefore, the pertinent features of the loop transients in the outer corona are basically gasdynamical. As a conspicuous part of coronal expansion, the motion of the compressible masses in the transient loops is largely controlled by thermal forces. The translational motion of heliocentrifugal expansion is driven by the hydrodynamic buoyant force, and the lateral motion of peripheral expansion is driven by the pressure difference between the dense plasma of the ejecta and the tenuous plasma of the ambient medium.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 71; May 1981
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  • 84
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    Decameter studies of the 5 September 1973 flare (1981)
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    Publication Date: 2019-06-28
    Description: The spectra and positions of the meter-decameter wavelength radio sources associated with the flare of September 5, 1973 are discussed. The evolution of the size of the type II burst source is discussed and it is shown that it fluctuates by a factor of 10, or larger. Consequently, the potential and kinetic energies associated with the shock are uncertain by the same factor. By a comparison of the positions of the type II and type III sources, it is concluded that while the shock wave associated with the type II was guided along high loops, the type III electrons were injected along open field lines which diverged within a short height in the corona. The characteristics of a particularly interesting type III burst with a low-frequency cut-off are discussed. It is argued that nearby loops were not disrupted by the shock and that the energetic electrons produced during the event must have been injected at several sites and guided along open field lines at large distances from the flare to produce type III bursts.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 71; May 1981
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  • 85
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    On the outburst of flare activity of 26 November, 1973 (1981)
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    Publication Date: 2019-06-28
    Description: The possible source of a strong 30 hour-long outburst of homologous flare activity, and an unusual growth and brightening of coronal loops in the active region McMath 12628, on the eastern solar hemisphere, on Nov. 1973, as seen from Skylab are analyzed. Prior to that date, not many flares and subflares in the region were associated with radio bursts. However, almost all flares after that date were accompanied by microwaves and type III bursts until the last flare of this kind appeared at 03:52 on the 27th. All the type III bursts were accompanied by type U-bursts, giving evidence for strong closed fields rooted in the site of the radio bursts. It is recorded that U-bursts stopped after 07:18 on Nov. 26, and a change noted is attributed to the occurrence of two two-ribbon flares at the site of the recurrent activity which could have destroyed the U-type favorable situation. A two-ribbon flare, according to Kopp and Pneuman (1976), opens the magnetic field-configuration, and it is therefore suggested that a newly emerging magnetic flux was the source of the complex solar situation. It is suggested that this kind of activity should be studied during the FBS-ALERT periods in 1980-81.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 71; May 1981
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  • 86
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    Umbral oscillations as resonant modes of magneto-atmospheric waves (1981)
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    Publication Date: 2019-06-28
    Description: Umbral oscillations in sunspots are identified as a resonant response of the umbral atmosphere to forcing by oscillatory convection in the subphotosphere. The full, linearized equations for magnetoatmospheric waves are solved numerically for a detailed model of the umbral atmosphere, for both forced and free oscillations. Resonant 'fast' modes are found, the lowest mode having a period of 153 s, typical of umbral oscillations. A comparison is made with a similar analysis by Uchida and Sakurai (1975), who calculated resonant modes using an approximate ('quasi-Alfven') form of the wave equations. Whereas both analyses give an appropriate value for the period of oscillation, several new features of the motion follow from the full equations. The resonant modes are due to upward reflection in the subphotosphere (due to increasing sound speed) and downward reflection in the photosphere and low chromosphere (due to increasing Alfven speed); downward reflection at the chromosphere-corona transition is unimportant for these modes.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 71; May 1981
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  • 87
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    H-alpha flare spectra (1981)
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    Publication Date: 2019-06-28
    Description: More than 1000 H-alpha flare profiles from 24 solar flares of Class 1 or brighter recorded with the multislit spectrograph of the Lockheed Solar Observatory are examined. It is found that the profiles can be classified in terms of whether or not they show central self-reversals, whether or not they have extended wings, and whether or not they are asymmetric. The profile groupings are not correlated with the size (class) of the flares, nor do they seem to be correlated with the type of chromospheric flare structure from which they are emitted. Although different flare points within the same overall event may show profiles of different types, any given element (bright patch) can usually be described in terms of a single combination of the profile descriptors.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 70; Apr. 198
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  • 88
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    X-ray and H-alpha observations of a filament-disappearance flare - An empirical analysis of the magnetic field configuration (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: On August, 29, 1973, a flare event occurred that involved the disappearance of a filament near central meridian. The event, well-observed in X-rays on Skylab and in H-alpha, was a four-ribbon flare involving both new and old magnetic inversion lines which were roughly parallel. The H-alpha, X-ray, and magnetic field data are used to deduce the magnetic polarities of the H-alpha brightening at the footpoints of the brightest X-ray loops. It is suggested that the event involved a reconnection of magnetic field lines rather than a brightening in place of preexisting loops. The simultaneity of the H-alpha brightening onsets in the four ribbons and the apparent lack of an eruption of the filament are consistent with this interpretation.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 70; Apr. 198
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  • 89
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    Coronal holes, solar wind streams, and geomagnetic disturbances during 1978 and 1979 (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: It was found that, during 1978 and 1979, coronal holes reflected the influence of differential rotation, and were present within a slowly evolving large-scale pattern in spite of the relatively high level of sunspot activity. The long-lived 28.5-day pattern is not produced by a rigidly rotating quasi-stationary structure on the sun, but appears to be produced by a nonstationary migratory process associated with solar differential rotation. The association between coronal holes and solar wind speed enhancements at earth continues to depend on the latitude of the holes (relative to the heliographic latitude of earth), but even the best associations since 1976 have speeds of only 500-600 km/s rather than the values of 600-700 km/s that usually occurred during the declining phase of sunspot cycle 20.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 70; Apr. 198
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  • 90
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    The isotopic composition of magnesium nuclei in solar flares (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 245
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  • 91
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    Ionization states of heavy elements observed in the 1974 May 14-15 anomalous solar particle event (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The charge states of heavy ions accelerated in the (He-3)-Fe-rich solar particle event of May 14-15, 1974 have been determined by the use of using data from the University of Maryland/Max-Planck-Institut experiment on IMP 8. In addition to Fe(+11,12), it is found that both O(+5) and Fe(+16,17,18) are also present, suggesting variations in coronal temperatures over a range from approximately 400,000 to 5,000,000 K. The presence of O(+5) and Fe(+16-18) may be explained by a resonant plasma heating mechanism proposed by Fisk (1978) to account for the enhancements of He-3 and Fe.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 245
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  • 92
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    The C I opacity and physical structure of cool, very dense plasma in the solar corona (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The physical structure of the cool material in the volume of the solar corona is investigated. The observational evidence is summarized in a table giving the brightness contrast in optical and EUV radiations. The state of ionization and the opacity sources are discussed, and a physical model is described that is consistent with the EUV and optical data. It is noted that a comparison of the EUV raster pictures with H-alpha and Ca K photoheliograms indicates that the material is commonly injected from below into relatively low-lying magnetic loops (fibrils) seen near sunspots and plages.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 245
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  • 93
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    Observations with the SMM gamma-ray spectrometer - The impulsive solar flares of 1980 March 29 (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Gamma-ray continuum emission from 0.3 to 1 MeV was observed with the gamma-ray spectrometer on the Solar Maximum Mission satellite during two impulsive solar flares on 1980 March 29, from active region 2363 at 0918 UT and from active region 2357 at 0955 UT. Evidence is presented for a hardening of the spectrum during the impulsive phase of the flares. The photon intensity greater than 100 keV appears to decay at a slower rate than that at lower energies. Time-integrated photon spectra for both flares are incompatible with a single-temperature thermal-bremsstrahlung model. Upper limits for prompt and delayed gamma-ray lines are presented.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 94
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    Variations of solar irradiance (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The active cavity radiometer experiment on the Solar Maximum Mission is providing sensitive measurements of time variations of the total solar irradiance with greater accuracy and precision than previously achieved. The mean 1 AU irradiance for the first 45 days' operation is 1368.64 W/sq m with an absolute uncertainty of less than + or 0.5%. Variations about this mean have been observed on time scales of hours to days with amplitudes up to + or - 0.04%, resolved with a statistical uncertainty as low as 0.001%. Variations within a single orbit with amplitudes as large as + or - 0.5% have been resolved with 0.005% or smaller statistical uncertainty. Although these variations do not display a systematic relationship to conventional solar activity indices over the period, correlative behavior cannot be ruled out on the basis of the present limited data set.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 95
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    Observation of the 2.223 MeV gamma-ray line on the SMM satellite - The event of 1980 June 7 (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 96
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    Observations of the limb solar flare on 1980 April 30 with the SMM X-ray polychromator (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 97
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    X-ray spectra of solar flares obtained with a high-resolution bent crystal spectrometer (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Preliminary results obtained for three solar flares with the bent crystal spectrometer on the SMM are presented. Resonance and satellite lines of Ca XIX and XVIII and Fe XXV and XXIV are observed together with the Fe XXVI Lyman-alpha line. Plasma properties are deduced from line ratios and evidence is presented for changes of line widths coincident with the occurrence of a hard X-ray impulsive burst. Fe K-alpha spectra from a disk center and a limb flare agree with the predictions of a fluorescence excitation model. However, a transient Fe K-alpha burst observed in a third flare may be explained by the collisional ionization of cool iron by energetic electrons.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 98
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    Radio and visible light observations of matter ejected from the sun (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An initial set of visible light and radio observations of a coronal transient made with the Coronagraph/Polarimeter experiment on SMM and the radioheliograph at Culgoora, Australia is presented. It is noted that an enormous loop-shaped transient observed on April 7, 1980, exhibited bright material having whiplike, nonradial motions, as well as moving and stationary radio sources. The data make it possible to establish that a moving type IV radio source was located on or very close to the fast-moving loop. The thermal, kinetic, and magnetic energies in the transient are estimated and, for the first time, compared with the radiative energy of the associated flare.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 99
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    Studies of the corona with the Solar Maximum Mission coronagraph/polarimeter (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The visible wavelength coronagraph/polarimeter on the Solar Maximum Mission (SMM) spacecraft is providing data on the flare processes manifested by coronal transients and on the degree of disruption of the evolutionary corona at the present epoch of the solar activity cycle. Among the first results are the discovery of frequent H-alpha emission from remnants of eruptive prominences in the outer corona and first observations of Fe XIV line emission to 3.2 solar radii. In the early stages of transients, cavities less dense than the ambient corona are occasionally found trailing the transient loops, with the loops being relatively thick and structureless. Some 22 transients have been identified in the initial survey of 52 days of observations; from this sample the preliminary conclusion is that transients during the SMM era (near solar maximum) occur over a wider range of latitude than, but with about the same range of speeds as, transients during the Skylab era (near solar minimum).
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 100
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    X-ray line widths and coronal heating (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Preliminary results of spectroscopy and imaging of a solar active region and flare plasma in soft X-ray emission lines are presented. Observed X-ray line widths in a nonflaring active region are broader than the Doppler width corresponding to the local electron temperature. An analysis of 41 soft X-ray flares within a single active region reveals a preference for flares to occur at locations that already show enhanced X-ray emission and to favor magnetic complexity over high gradient. However, flares do not appear to be directly responsible for the heating and X-ray production of the active regions.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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