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  • Other Sources  (252)
  • SOLAR PHYSICS  (252)
  • 1980-1984  (252)
  • 1950-1954
  • 1982  (252)
  • 1950
  • 1
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    Energetic electrons associated with solar radio storms (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: SOLAR PHYSICS
    Type: Osservatorio Astronomico Solar Radio Storms. Proc. of the 4th CESRA Workshop on Solar Noise Storms; p 320-323
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  • 2
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    Solar radio storms in the hectometer-kilometer wavelength range (1982)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: SOLAR PHYSICS
    Type: Osservatorio Astronomico Solar Radio Storms. Proc. of the 4th CESRA Workshop on Solar Noise Storms; p 70-88
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  • 3
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    Solar variability (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The variability in the total radiant energy flux, or solar irradiance, is discussed. Direct techniques of measuring irradiance, including ground-based, balloon and rocket-borne, and spacecraft-based measurements are compared; the latter type has led to dramatic advances in accuracy since it eliminates the need for corrections for atmospheric absorption. Correlations of the measured irradiance with solar activity are described. Indirect techniques that monitor other solar parameters such as photospheric conditions or the solar diameter are reviewed, and theoretical studies which attempt to interpret the measurements are discussed. Physical mechanisms which can lead to changes in the solar luminosity are addressed, as is global time-dependent modeling of the response of the sun to structural perturbations. Finally, findings from all techniques are summarized, their weak and strong points are assessed, and suggestions for future research are made.
    Keywords: SOLAR PHYSICS
    Type: Comments on Modern Physics; vol. 9
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  • 4
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    Measurement of the rugged invariants of magnetohydrodynamic turbulence in the solar wind (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Measurements of the total energy, cross helicity, and magnetic helicity of the solar wind at 1, 2.8, and 5 AU are presented. These quantities are the three rugged invariants of three-dimensional ideal incompressible MHD turbulence theory. The theoretical technique for measuring the magnetic helicity from the matrix of two-point correlations is shown. The length scales characterizing the magnetic helicity are found to be equal to or greater than those which characterize the magnetic energy. The magnetic helicity typically lies at scales larger than the magnetic correlation length, consistent with the expectations of the inverse cascade and selective decay hypotheses of three-dimensional MHD turbulence. At smaller scales, the magnetic helicity oscillates in sign. Measurements of the cross helicity are not fully consistent with the usual interpretation in terms of outward propagating Alfvenic functions. Especially during the interval at 5 AU the cross helicity is found to oscillate in sign indicating fluctuations propagating both outward and inward.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Aug. 1
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  • 5
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    Type II solar radio events observed in the interplanetary medium. I - General characteristics (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N81-15927)
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 78; May 1982
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  • 6
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    S IV emission-line ratios in the sun (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: New atomic data are presented for transitions between the five lowest levels in S IV, taking into account the fine-structure rates between the individual J levels together with the electron impact mixing rates within the levels. The values are found to differ significantly from previously published values. Using the atomic data, ionic level populations are deduced for a range of electron temperatures and densities. The results are used to calculate theoretical line intensity ratios for S IV. Excellent agreement is found with intensity ratios for a variety of solar features observed with the NRL normal incidence spectrograph on Skylab.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 257
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  • 7
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    Solar irradiance variations due to active regions (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Questions regarding changes in solar irradiance due to activity are important, since such changes may have a significant effect on the earth's climate. Solar irradiance measurements conducted outside the earth's atmosphere and, therefore, not affected by it have become possible by utilizing for such measurements satellites, such as the Nimbus 7 and the Solar Maximum Mission satellite (ACRIM experiment). The present investigation has the objective to show that a combination of sunspots and faculae is capable of representing the observed variations in the values of ACRIM data to a satisfactory degree, given the current level of uncertainties in the ground-based data.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 256
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  • 8
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    Radial variation of the solar wind speed between 1 and 15 AU (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Pioneer 10 and 11 solar wind speeds measured between 1.4 and 15.2 AU are compared with those of IMP 6, 7, and 8 measured at 1 AU for 90-day intervals centered on six solar radial alignments between 1973 and 1978. The time profile of the solar wind speed undergoes change as the distance from the sun increases, which is due to interaction of adjacent solar wind streams. Speed variations are smaller at greater radial distance and both the highest and lowest speeds disappear as radial distance increases. For periods with extremely high speed solar wind streams, the mean solar wind speed decreases as the distance from the sun increases, which must be due to the disappearance of the highest speeds of the streams with increasing distance. It is concluded that at distances from the sun greater than 30-40 AU, the solar wind behavior may closely resemble that of a radially expanding constant speed plasma.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Apr. 1
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  • 9
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    Measurement of the profile of solar He I resonance lines (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The analysis of data obtained by a rocket-borne helium-filled spectrometer employing a curve-of-growth technique in 1977 and 1980 is used in an investigation of the 584-A helium resonance line from the full solar disk. Between 6.5 and 13% of the Gaussian core area was found to be missing through self-reversal. Line widths from 1980 and 1977 were 101 + or - 10 mA and 128 + or - 20 mA full width at half maximum, respectively. No consistent relationship is found between the measured widths and solar activity.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Mar. 1
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  • 10
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    Fluid motions the solar chromosphere-corona transition region. II Active region flows in C IV from narrow slit Dopplergrams (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 261
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  • 11
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    Mass motions in the solar chromosphere and transition zone (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A comparison is made between H-alpha and C IV observations of Active Region 2717 on October 9, 1980. On the basis of this comparison, it is found that upward velocities are present above sunspots in the chromosphere-corona transition zone (20 km/s). The downward velocities are found to be well correlated in both lines. Doppler-shift ratios between C IV and H-alpha levels (approximately 10) are seen to be much smaller than expected from density ratio estimates. The comparison is seen as suggesting that flow lines are probably far from vertical in the transition zone. It is pointed out, however, that this depends on model densities that may not be correct. A simple method for comparing matter flows is presented. The best fit between H-alpha and C IV levels is obtained when C IV Doppler shifts are multiplied by the line intensity to the power 0.5 (approximately) in order to make allowance for density fluctuations.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 111; 1, Ju; July 198
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  • 12
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    The solar spectrum of O IV, including photoexcitation by Fe IX 171.07 A (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The extreme and far ultraviolet doublet spectrum of O IV, emitted from the solar transition region, is calculated taking account of expected photo-excitation by Fe IX at the wavelength 171.07 A. Four multiplets are shown to be sensitive to such photoexcitation, of which two in particular are potentially observable and could provide an estimate of the local Fe IX radiation field.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 108; 2, Ap; Apr. 198
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  • 13
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    Spatial and temporal evolution of soft and hard X-ray emission in a solar flare (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Hard X-ray burst spectrometer and imaging spectrometer data are used to study the spatial and temporal characteristics of the 3.5-30.0 keV emission in an Apr. 10, 1980 solar flare. It is found that: (1) continuous energy release is needed to sustain the increase of the emission through the flare's rising phase, before and after the impulsive phase in hard X-rays, and the release is characterized by the production of 50 million-150 million K thermal regions within the flare loop structures; (2) the observational parameters which characterize the impulsive burst indicate that it is probably associated with nonthermal processes, such as particle acceleration; and (3) the continuous energy release is associated with strong chromospheric evaporation, in view of spectral line behavior. Both particle acceleration and chromospheric evaporation stop just before flare maximum, and the subsequent evolution is probably governed by the radiative cooling of the flare plasma.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 79; July 198
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  • 14
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    The solar O III spectrum. I - Photoexcitation of EUV lines by He II Lyman-alpha (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 257
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  • 15
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    Statistical properties of MHD fluctuations associated with high-speed streams from Helios-2 observations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-18117)
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 78; June 198
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  • 16
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    Latest rocket measurements of the solar constant (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Three rocket flights which carried a payload of absolute radiometers to measure the solar constant with an accuracy of plus or minus 0.5 per cent have been accomplished. Several of the rocket radiometers were duplicates of those aboard the Solar Maximum Mission and Nimbus spacecrafts. The values for the solar constant obtained by the rocket sensors for the three flight dates indicate an increase between the first and latter two flights approximately equivalent to the uncertainty of the measurements. The values for the solar constant for the three flights are 1367, 1372 and 1374 W/sq m.
    Keywords: SOLAR PHYSICS
    Type: Solar Energy; 28; 5, 19; 1982
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  • 17
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    Solar irradiance variations and solar activity (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A mean value for the 1 AU total solar irradiance of 1368.2 W/sq m and a downward trend of 0.05% per year were derived from measurements by the Active Cavity Radiometer Irradiance Monitor (ACRIM) experiment on the Solar Maximum Mission during 1980. Distinct temporary solar irradiance decreases associated with solar activity maxima were observed with a series of nine dips from April to October recurring at fairly regular intervals averaging 24 days. The decreases correlate inversely with sunspot area, 2800-MHz flux, and Zurich sunspot number. Dominant periods common to the irradiance and sunspot area power spectra link the irradiance decreases to sunspot flux deficit in solar active regions. Evidence of significant total irradiance modulation by facular flux excess is cited. A persistent radiative cycle of active regions consistent with the ACRIM irradiance results and the morphology of solar active regions was found. The pattern of regularly recurrent active region maxima between April and October suggests an asymmetry in solar activity generation during this period.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; June 1
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  • 18
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    Solar transition region response to variations in the heating rate (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The response of a numerical model for the upper chromosphere, transition region, and corona to variations in the energy input has been examined. The numerical model solves the set of one-dimensional two-fluid hydrodynamic equations in a simple vertical magnetic flux tube. The atmosphere responds to both the increase and decrease in energy deposition by smoothly readjusting the temperature gradient and the amount of material in the region of peak radiating efficiency to radiate away energy being deposited. At no time during this readjustment is a departure from a thin laminar transition region structure seen. In addition, a time-dependent description of the nonequilibrium ionization of all of the ionization stages of oxygen has been included. This calculation is coupled with the self-consistent calculations of the dynamical variables. It is found that the nonequilibrium ionization balance calculations for both heating and cooling small loops in the quiet sun predict relative ionic abundances which differ substantially from those which would be predicted by an equilibrium calculation
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 255
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  • 19
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    Doppler wavelength shifts of ultraviolet spectral lines in solar active regions (1982)
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    Publication Date: 2011-08-18
    Description: Doppler shifts are measured for solar UV emission lines formed in the lower transition region of active regions. Doppler shifts in different regions at the same solar location, variations of Doppler shift with position of an active region on the disk, and variations of Doppler shift with time at the same solar location in the same active region were studied. Observations were made with the NRL slit spectrograph on Skylab. Excluding flare and flare-related phenomena, only redshifts are found whose magnitudes correspond to downflow velocities between about 4 and 17 km/s. Shifts are largest for lines formed between about 50,000 and 100,000 K, and are distinctly less for lines formed above 100,000 K. The shifts persist out to the limb, but not above it. There is no obvious change in redshift for lines measured at the same solar location over time intervals of about 20 minutes.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 255
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  • 20
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    Ultraviolet continuum absorption /less than about 1000 A/ above the quiet sun transition region (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Lyman continuum absorption shortward of 912 A in the quiet sun solar transition region is investigated by combining spectra obtained from the Apollo Telescope Mount experiments on Skylab. The most recent atomic data are used to compute line intensities for lines that fall on both sides of the Lyman limit. Lines of O III, O IV, O V, and S IV are considered. The computed intensity ratios of most lines from O IV, O V, and S IV agree with the experimental ratios to within a factor of 2. However, the discrepancies show no apparent wavelength dependence. From this fact, it is concluded that at least part of the discrepancy between theory and observation for lines of these ions can be accounted for by uncertainties in instrumental calibration and atomic data. However, difficulties remain in reconciling observation and theory, particularly for lines of O III, and one line of S IV. The other recent results of Schmahl and Orrall (1979) are also discussed in terms of newer atomic data.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 254
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  • 21
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    The condensational instability in the solar transition region and corona (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The stability of plasmas at temperatures and densities typical of the solar transition region and corona is investigated using both a linear analysis and nonlinear time-dependent numerical simulations. Growth rates, decay rates, and oscillation frequencies of the perturbations determined from the linear analysis are in excellent agreement with the simulations. The nonlinear regime is characterized by a bifurcation of the plasma into a cool dense condensation surrounded by a hot tenuous corona. The condensation may then be accelerated by forces in the plasma such as those arising from gravity or differential heating. Finally, the results of the detailed simulation show that the transition region is a dynamically stable structure which is the result of the nonlinear evolution of the condensational instability.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 254
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  • 22
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    Transition region oscillations in sunspots (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Time series observations of the profile of the C IV resonance line 1548.19 A obtained in eight sunspots with the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission are discussed. All of the sunspots exhibit significant oscillations in line-of-sight velocity with frequencies in the range from 5.8 mHz to 7.8 mHz (periods of 129-173 s). Significant intensity oscillations are observed at the same periods in four of the time series; the maximum intensity is in phase with maximum blueshift. Difference spectroheliograms ('Dopplergrams') of the two halves of the C IV line, as well as observations in the Si IV resonance line 1402.77 A and the O IV intersystem line 1401.16 A, also reveal velocity oscillations at similar frequencies but only over sunspots.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 253
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  • 23
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    The vertical filamentary structures of quiescent prominences (1982)
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    Publication Date: 2011-08-18
    Description: The thin vertical filaments making up the quiescent prominence plasma, as revealed by fine spatial resolution H-alpha photographs, are characterized by a magnetostatic theory in which a horizontal row of long vertical filaments whose weights are supported by bowed magnetic field lines is described by a class of exact equilibrium solutions. The Kippenhahn-Schlueter (1957) solution for a long sheet without filamentary structures is a member of this class of solutions. In illustrating the role of the magnetic field in supporting and thermally shielding the filament plasma, it is found that the filament can have a sharp transition perpendicular to the local field, while the transition in the direction of the local field is diffuse. A consequence of the filamentary structure is that its support by the Lorentz force requires the electric current to have a component along the magnetic field.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 75; Jan. 198
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  • 24
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    A surge observed in H alpha and C IV (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results are presented of simultaneous measurements of H-alpha (MSDP at Meudon) and C IV (UVSP onboard SMM) of Active Region 2701 made on October 2, 1980. Isodensity and velocity maps were obtained for both lines and these maps were superimposed. Results show a good correlation between the H-alpha and C IV velocities with a surge being observed for 10 minutes. The base of the surge was determined to be located in a bright point in C IV and H-alpha, while the escaping matter followed the same channel ('absorbing' in H-alpha, 'emitting' in C IV). It was found that the velocity along the surge was about 80 km/s in H-alpha and 100 km/s in C IV. In addition, a loop appeared in C IV during the surge. It is concluded that the vertical pressure gradient was capable of driving the surge.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 25
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    About the onsets of closely-consecutive homologous flares (1982)
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    Publication Date: 2011-08-18
    Description: The onsets of closely consecutive homologous flares (CCHF), which are separated by less than 6 hours and most often by about 1 hour, are compared with that of isolated flares (no flare in the region half a day before). Isolated flares appear to be formed of two components, a surging arch and a flaring arch, while a set of CCHF may be composed of consecutive elementary flares or of a series of complex ones. It is shown that the onset of eruptive flare phenomena is not the same for an isolated event and for a member of CCHF (excluding the first) as found in H-alpha and EUV observations, and probably in X-ray observations also. It is suggested that a CCHF set would become a single flare with episodic enhancement of brightness by taking account of the common H-alpha behavior of surging and flaring arches as well as the EUV emission.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 26
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    Observations of the longitudinal magnetic field in the transition region and photosphere of a sunspot (1982)
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    Publication Date: 2011-08-18
    Description: The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacraft has observed for the first time the longitudinal component of the magnetic field by means of the Zeeman effect in the transition region above a sunspot. The data presented here were obtained on three days in one sunspot, have spatial resolutions of 10 arcsec and 3 arcsec, and yield maximum field strengths greater than 1000 G above the umbrae in the spot. The method of analysis, including a line-width calibration feature used during some of the observations, is described in some detail in an appendix; the line width is required for the determination of the longitudinal magnetic field from the observed circular polarization. The transition region data for one day are compared with photospheric magnetograms from the Marshall Space Flight Center. Vertical gradients of the magnetic field are compared from the two sets of data; the maximum gradients of 0.41 to 0.62 G/km occur above the umbra and agree with or are smaller than values observed previously in the photosphere and low chromosphere.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 81; Dec. 198
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  • 27
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    Stationarity of magnetohydrodynamic fluctuations in the solar wind (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N83-11007)
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Dec. 1
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  • 28
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    A three-component model of the variability of the solar ultraviolet flux 145-200 nM (1982)
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    Publication Date: 2011-08-18
    Description: The variability of the ultraviolet flux between 145 and 200 nm over both the eleven-year cycle and the 27-day solar rotation period is examined in terms of chromospheric activity, as determined from ground-based observations of the CaII K chromosphere. A three-component model of the solar UV flux is developed which includes the contributions to the full disk flux from both plage and active network emission. Solar cycle and solar rotation variations derived from the model are compared with the results of satellite and rocket experiments and with the two-component model of Cook et al (1980). Finally, possible ways of improving the model are discussed.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Dec. 1
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  • 29
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    Active-region evolution and solar rotation variations in solar UV irradiance, total solar irradiance, and soft X rays (1982)
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    Publication Date: 2011-08-18
    Description: Variations in the total solar irradiance, solar UV spectral irradiance, and solar soft X-ray emission caused by active region evolution and solar rotation are analyzed by using concurrent measurements from the NIMBUS 7 and GOES satellites. The observations are interpreted by using simple empirical models that relate ground-based observations of the size and location of sunspots and plages to the full-disk temporal variations. It is found that the major dips in the photospheric total solar irradiance S, which are evident in both satellite measurements and model predictions, are usually not accompanied by outstanding enhancements in the chromospheric and upper photospheric UV spectral irradiance or coronal X rays. The main cause of this difference between the variability of S and of the UV flux is that the total chromospheric plage enhancements are not outstanding at those times when the total sunspot are outstanding. X rays are even more variable because of a much wider CMD sensitivity.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Dec. 1
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  • 30
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    Magnetic clouds - Voyager observations between 2 and 4 AU (1982)
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-13593)
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 81; Nov. 198
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  • 31
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    Proposed Mg V, Fe XIV and forbidden Fe XVII line identifications in the EUV solar spectrum (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 81; Nov. 198
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  • 32
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    Dynamics of the eruptive prominence of 6 May 1980 and its relationship to the coronal transient (1982)
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    Publication Date: 2011-08-18
    Description: The active prominence of the 6 May 1980 has been observed between 5.23 and 10.22 UT with the Ultraviolet Spectrometer and Polarimeter (UVSP) on board the Solar Maximum Mission (SMM) satellite. Intensities of 1548 A line of CIV and dopplershifts have been derived. A motion of the magnetic tube maintaining the prominence material is noted. This motion is followed by a coronal transient observed with the Coronagraph and Polarimeter (C/P) between 11 and 13 UT. It is suggested that the event is related to a MHD wave induced by a flare occurring behind the solar disk, and a MHD modeling of the perturbation is proposed.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 114; 1, Oc; Oct. 198
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  • 33
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    The structure, stability and flaring of solar coronal loops (1982)
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    Publication Date: 2011-08-18
    Description: A review is given of recent progress in the theory of the magnetohydrodynamic behavior of coronal loops, beginning with a brief characterization of thy observations. The equilibrium magnetic field is described, along with the consequences of the empirical requirement for short-term, or infinite-conductivity, stability which is shown to be dominated by the end-effect influence of thy quasi-rigid photosphere. A new loop-flare model is then developed, which takes account of the finite loop length. The primary resistive-sausage-mode instability exhibits the necessary threshold behavior, and produces a number of spatially and energetically distinct flare-release manifestations.
    Keywords: SOLAR PHYSICS
    Type: Societa Astronomica Italiana; vol. 53
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  • 34
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    Quadrupole distortions of the heliospheric current sheet in 1976 and 1977 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Latitudinal variations in the position of the heliospheric current sheet were investigated using interplanetary measurements from Helios A, Helios B, IMP 8, and white light corona measurements in the period May 1976 to May 1977. The latitude of the heliospheric current sheet between 0.3 AU and I AU is consistent with that of the maximum brightness curve of white light polarization brightness at 1.75 solar radii within approximately + or - 7 deg. The combined data sets show that the four-sector magnetic sector pattern observed in the ecliptic plane for most of this epoch could be attributed to a warped current sheet whose shape near the sun resembles a saddle surface that is nearly symmetrical about the equatorial plane. The latitudinal extent of the current sheet is on the average 8 deg and the maximum extent is 15 deg (except on one rotation, when it is 20 deg). These results can be interpreted as a consequence of the solar magnetic field, the dominant components of the field being due to a dipole nearly aligned with the sun's spin axis and a quadrupole component whose strength is about 17 percent of the dipole.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Dec. 1
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  • 35
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    Measurements of solar transition zone velocities and line broadening using the ultraviolet spectrometer and polarimeter on the Solar Maximum Mission (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The UVSP instrument on SMM is able to observe solar regions at two wavelengths in the same line with a band-pass of 0.3 A. Intensity and Doppler velocity maps are derived. It is shown that the numerical values are sensitive to the adopted Doppler width and the range of velocities is limited to within 30 km/sec. A method called Double Dopplergram Determination (DDD) is described for deriving both the Doppler width and the velocity (up to 80 km/sec), and the main sources of uncertainties are discussed. To illustrate the method, a set of C IV 1548 A observations is analyzed according to this procedure. The mean C IV Doppler width measured (0.15 A) is comparable to previous determinations. A relation is found between bright regions and down-flows. Large Doppler widths correspond to strong velocity gradients.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 115; 2, No; Nov. 198
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  • 36
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    A dispersion law for solar oscillations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The simple model of p-mode solar oscillations of Liebacher and Stein (1981), in which the acoustic vibrations are trapped in a resonant cavity taking the form of a spherical shell below the solar surface, is compared with Doppler shift observations of vertical velocities. The model is shown to predict a modified dispersion law in which the sound travel time across the cavity is a function of the ratio of the temporal frequency to the horizontal wavenumber, resulting in a single curve when the temporal frequency is plotted against the wavenumber. Frequencies derived from a two-dimensional power spectrum of velocity observations are found to conform to a modified version of the dispersion relation, and that only when the fundamental mode is excluded. Results thus suggest that all modes with the same frequency/wavenumber ratio are trapped in an identical cavity, or, more plausibly, that the difference in upper boundary conditions for different modes has minimal effect on the resulting frequencies.
    Keywords: SOLAR PHYSICS
    Type: Nature; 300; Nov. 18
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  • 37
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    Flare buildup in X-rays, UV, microwaves and white light (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Coordinated observations using space and ground-based instruments were made of active region complex numbers 2522/2530, 24-30 June, 1980. The 10 largest flares from these regions were of importance M1-M6 in X-rays, and all were observed from satellites, except for one observed from a balloon. Several kinds of buildup signature have been found in the tens of minutes before these flares. Among these signatures are the following: (1) relative faintness in X-ray lines of the pre-flare pixels, (2) X-ray (5-15 keV) 'flashes' at points displaced by 1-2 arcmin from the flare site, (3) rising filaments seen in H-alpha and ultraviolet, (4) microwave intensification, polarization increase, and polarization flip, and (5) coronal disturbances above limb flares at or before the impulsive phase.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 38
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    Flare build-up study: Homologous flares group - Interim report (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: When homologous flares are broadly defined as having footpoint structures in common, it is found that a majority of flares fall into homologous sets. Filament eruptions and mass ejection in members of an homologous flare set show that maintainance of the magnetic structure is not a necessary condition for homology.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 39
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    Particle acceleration by coronal and interplanetary shock waves (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Utilizing many years of observation from deep space and near-earth spacecraft a theoretical understanding has evolved on how ions and electrons are accelerated in interplanetary shock waves. This understanding is now being applied to solar flare-induced shock waves propagating through the solar atmosphere. Such solar flare phenomena as gamma-ray line and neutron emissions, interplanetary energetic electron and ion events, and Type II and moving Type IV radio bursts appear understandable in terms of particle acceleration in shock waves.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 40
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    A magnetic cloud and a coronal mass ejection (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An interplanetary magnetic cloud observed by the Helios 1 spacecraft was found to be associated with a coronal mass ejection observed by the NRL Solwind coronagraph on the spacecraft P78-1. The magnetic cloud was observed on June 20, 1980, when Helios 1 was at 0.54 AU and nearly 90 deg west of the earth-sun line. This was associated with a large loop-like coronal mass ejection observed over the west limb on June 18, 1980, moving toward Helios 1. The speed of the front of the event at Helios 1 was (470 + or - 10) km/s, which is close to the mean transit speed (approximately 500 km/s). The magnetic cloud was similar to others described in the literature: The magnetic field strength was higher than average; the density was relatively low; the magnetic pressure greatly exceeded the ion thermal pressure; and the magnetic field direction changed through the cloud by rotating parallel to a plane which was highly inclined with respect to the ecliptic.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters; 9; Dec. 198
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  • 41
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    Scaling-law equilibria for calcium in canopy-type models of the solar chromosphere (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Scaling laws for resonance line formation are used to obtain approximate excitation and ionization equilibria for a three-level model of singly ionized calcium. The method has been developed for and is applied to the study of magnetograph response in the 8542 A infrared triplet line to magnetostatic canopies which schematically model diffuse, nearly horizontal fields in the low solar chromosphere. For this application, the method is shown to be efficient and semi-quantitative, and the results indicate the type and range of effects on calcium-line radiation which result from reduced gas pressure inside the magnetic regions.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 79; Aug. 198
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  • 42
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    Hydromagnetic stability of coronal arcade structures The effects of photospheric line tying (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A model is given of the magnetic-field equilibrium and possible dynamic excitations of a solar coronal arcade. Such structures are well observed in the spectral range from H-alpha to X-rays and often give rise to two-ribbon flares. However, the preflare state must be stable to ideal magnetohydrodynamic disturbances, and this problem is treated with particular attention to the necessary foot-point boundary conditions. With reasonably general perturbation set, an energy-principle analysis is used to show the strong stabilizing influence of inertial field-line tying at the photosphere.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 79; Aug. 198
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  • 43
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    The three-dimensional structure of atmospheric magnetic fields in two active regions (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The magnetic field above two unrelated active regions on September 11-12, 1974 has been studied by means of magnetograms obtained in C I 9111, Fe I 8688, Ca II 8542, and H-alpha. In C I, originating low in the photosphere, the fields are strong and sharply defined, by contrast with Ca II and H-alpha, where they are very diffuse. The similar diffuseness of Fe I is due to the spreading of the field with height to form nearly horizontal magnetic canopies over regions free of field at lower levels. Within a region between two small sunspots some 140 Mm apart, the canopy height is typically 300-400 km, and it is about 150-250 km within a small superpenumbra. It is hypothesized that the chromospheric fibrils taken to delineate the field configuration are not due primarily to lateral variations in field, but rather to differences in density or excitation of gas across the lines of force.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 79; Aug. 198
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  • 44
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    Magnetograph response to canopy-type fields (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The response of longitudinal-field magnetographs to magnetic fields which are semi-infinite or confined to a horizontal layer is discussed with respect to the interpretation of solar diffuse fields, observed towards the limb, in terms of magnetic canopy models. Numerical results are presented for several reference solar models and typical 'calibration' curves are shown for the CI 9111 A, Fe I 8688 A, and Ca II 8542 A lines in magnetostatic atmospheres derived from a mean model. A procedure is developed for determining the base heights of magnetic canopies from observations with an uncertainty not exceeding the order of a pressure scale height. Until definitive information regarding atmospheric structure inside flux tubes can be developed from theory or observation, reliable field strengths cannot be derived from the data.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 79; Aug. 198
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  • 45
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    Evidence for a poleward meridional flow on the sun (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Two subsets of all polar zone filaments, designated polemost filament and polar filament bands, are defined for observational study of their behavior, which is compared with the evolution of the polar magnetic field over Howard and LaBonte's (1981) activity cycle. The magnetic data show that the polar magnetic fields are built up and maintained by the episodic arrival of discrete f-polarity regions originating in active region latitudes and subsequently drifting to the poles. F-polarity regions are carried poleward by a meridional flow, rather than by diffusion. It is noted that the mean latitude of the polemost filaments tracks the boundary of the polar field cap, and undergoes an equatorward dip during each arrival of additional polar field, and that the polar filament bands track the boundary latitudes of the unipolar regions, drifting poleward with the regions at about 10 m/sec.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 79; Aug. 198
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  • 46
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    Unusual coronal activity following the flare of 6 November 1980 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The major two-ribbon flare that occurred on November 6, 1980 is discussed, using data from the hard X-ray imaging spectrometer aboard the SMM satellite. The post-flare X-ray arch and loops are analyzed, showing the flare characteristics, the coronal arch, the time variations of X-rays after the flare, and the time variation of the maximum intensity at the top of the coronal arch in the 3.5-5.5 keV range. A comparison is made with an earlier arch. The post-flare conronal brightness variations are discussed, including a correlation with a 169 MHz noise stomr, the absence of chromospheric excitation, the brightness and temperature of the X-ray arch, the locations of the brightenings, and the details of the first and fifth brightenings. Problems posed by the observations are discussed.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 80; Sept
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  • 47
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    Solar irradiance modulation by active regions during 1980 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The solar irradiance modulation due to active regions during 1980 has been investigated in detail. Specifically, the uncertainties caused by ground-based data used as input in the modeling effort, and by currently incomplete knowledge of the proper parameters that describe the angular variation of sunspot and facular contrasts are estimated. It is concluded that the most significant uncertainties are due to errors in area measurements and, possibly, varying spot and facular brightness. A 'standard model' for later use is derived to a best-fit technique of the currently available ACRIM irradiance data and the predictions of models with appropriately varied parameters. Finally, the expected irradiance for the entire year of 1980 is computed.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 80; Sept
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  • 48
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    The dynamics of accelerating coronal bullets (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results are presented of computer simulations of the jets that accelerate through the corona at velocities of 50 to 400 km/s. Particular emphasis is placed on the sensitivity of the induced acceleration to the form in which energy is put into the system. A comparison is made between the observed and predicted physical characteristics of the high-velocity bullets; the potential contribution of the bullets to the mass and energy balance of the solar corona is considered. It is found that the velocity and temperature evolution of the bullets can be modeled successfully by assuming energy input in the form of an external force, pushing continuously on the ejected material. From the physical characteristics of the model bullets and the energy input required to reproduce the observations, it is concluded that the bullets may constitute a significant fraction of the coronal mass flux but only a negligible component of the coronal energy budget.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 261
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  • 49
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    High-resolution X-ray spectra of solar flares. VI - Impulsive soft X-ray flares (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Doschek et al. (1980) and Feldman et al. (1980) have discussed high-resolution soft X-ray spectra of solar flares. The present investigation is concerned with the characteristics of the impulsive events as observed in soft X rays and the cooling of the flare plasma in terms of energy loss processes. A class of intense, short-lived solar flares which appear to be characterized by very high densities at high temperatures is found. For the 1979 November 6 event, the cooling time is so rapid that the density obtained may be a lower limit. The main cooling mechanism for the flares is found to be radiative. Two of the events are associated with strong gamma-ray emission and both of these events are very unusual in their soft X-ray emission. The 1979 November 9 flare shows extremely broad X-ray emission lines during the rise phase, indicative of nonthermal velocities of the order of 300 km/s.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 260
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  • 50
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    Quantitative tests of a steady state theory of solar wind electrons (1982)
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    Publication Date: 2011-08-18
    Description: A comparison is made of IMP 6, 7 and 8 electron data with the predictions of a solar wind electron steady state theory in which the control of transport by the macroscopic interplanetary electric and magnetic fields, as well as elastic Coulomb collisions with solar wind protons and thermal electrons, is assumed. While a ratio of forward to backward phase density for field-aligned extrathermal electrons of 6:1 is predicted, electron distribution measurements within the high speed solar wind show this ratio to be typically about an order of magnitude larger. A set of solar wind bulk speed anticorrelations predicted by the theory on the basis of a larger set of assumptions cannot be found in the IMP electron data set, so that improved agreement may require such modifications of the theory's assumptions as the inclusion of inelastic Coulomb and/or wave electron collisions.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Sept. 1
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  • 51
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    Magnetic energy storage and conversion in the solar atmosphere (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N81-33114)
    Keywords: SOLAR PHYSICS
    Type: Space Science Reviews; 31; 4, 19; 1982
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  • 52
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    Observational constraints for a theoretical model describing the soft X-ray flare (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: High-resolution solar flare X-ray spectra have recently been obtained from X-ray spectrometer experiments flown on an Air Force spacecraft (P78-1) launched on 1979 February 24. Interpretation of the spectra has produced new results concerning the physical conditions and time behavior of the thermal soft X-ray emitting plasma at temperatures near 20,000,000 K. It is argued that soft and hard X-ray events are not causally related to each other, but are simply two different manifestations of flare energy release. They probably occur in different plasma volumes. The source of the preflare plasma appears to be in the cooler parts of the solar atmosphere, perhaps transition region loops with initial temperatures of 100,000 K and densities of 10 to the 11th per cu cm. Continuous energy input, rather than sequential activation of loops, is required to explain the observations. Compression coupled with chromospheric ablation may produce the high densities in coronal flare loops.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 255
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  • 53
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    Observations of solar flare transition zone plasmas from the Solar Maximum Mission (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The spatial and temporal evolution of the Si IV and O IV intensity, density and mass motions in preflare and flare transition zone plasmas are studied for the case of the April 8, 1980 flare. It is found that: (1) the UV flare observed in the Si IV and O IV lines is unambiguously identified as occurring in a low-lying, preexisting transition zone loop which spanned the magnetic neutral line separating a larger leader spot and a newly emerged, isolated spot of opposite polarity; (2) at the onset of the flare, the easternmost footpoint, which was anchored in an isolated spot region of high longitudinal magnetic field gradient, showed sudden, impulsive brightening with large intensity increases; and (3) the release flare energy was transported by way of large-scale connecting field lines to other parts of the active region, producing the hot plasma and H-alpha kernels observed near the trailing spot.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 253
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  • 54
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    Recurrence of solar activity - Evidence for active longitudes (1982)
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    Publication Date: 2011-08-18
    Description: It is pointed out that the autocorrelation coefficients of the daily Wolf sunspot numbers over a period of 128 years reveal a number of interesting features of the variability of solar activity. Besides establishing periodicities for the solar rotation, solar activity cycle, and, perhaps, the 'Gleissberg Cycle', they suggest that active longitudes do exist, but with much greater strength and persistence in some solar cycles than in others. Evidence is adduced for a variation in the solar rotation period, as measured by sunspot number, of as much as two days between different solar cycles.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 76; Feb. 198
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  • 55
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    The equatorial photospheric rotation rate (1982)
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    Publication Date: 2011-08-18
    Description: The equatorial photospheric rotation rate was observed on 14 days in 1978-1980. The resulting rate, 14.14 + or - 0.04 deg/day, is found to be 2% slower than the rate observed for long-lived sunspots. Tables giving sidereal equatorial rotation rates measured with the line 10905 A Cr I and 6315 A Ni I are included.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 76; Feb. 198
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  • 56
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    Quick matching technique to study the relationship between solar radius and luminosity variations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A simple matching technique is developed which makes it possible to compute the response of the solar envelope to perturbations which occur within the solar convective region in timescales of importance to climate. The technique is applied to perturbation of the convective efficiency (alpha-mechanism) and of the nongas component of the pressure in different regions of the convection zone (beta-mechanism). The results indicate that whereas either perturbation affects the solar luminosity, the alpha-mechanism has almost no effect on the solar outer radius, regardless of the affected region. The beta-mechanism, however, produces radius changes which may be large if the location of perturbation is deep enough.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 76; Feb. 198
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  • 57
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    Solar irradiance modulation by active regions from 1969 through 1980 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The solar irradiance variations resulting from sunspot deficits and facular excesses in emission have been calculated from 1969 through 1980. Agreement appears to exist between the calculations and the major features seen with the Nimbus 7 cavity pyrheliometer and with both the major and minor features detected by the Solar Maximum Mission ACRIM experiment. The 12-year irradiance variations calculated suggest a larger variance with increased solar activity, and little change in the average irradiance with solar activity. The largest excursions over these 12 years show a 0.4% variation. Removal of the activity influences upon solar irradiance during the numerous rocket experiments observing the solar constant may allow a better value for this quantity to be determined.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters; 9; Jan. 198
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  • 58
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    Serf studies of mass motions arising in flares (1982)
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    Publication Date: 2019-06-28
    Description: It is believed that radio type IVs, co-spatial with dense hot plasmoids, may be the result of a plasma radiation emission mechanism. The injection of mass into the corona was recently observed in chromospheric and coronal lines with magnetic field changes and also at very high speeds into loops. The start time of coronal loop transients, if extrapolated to the chromosphere, in most cases precedes flare H-alpha or X-ray emission. Observational inferences from polarization and other studies are seen as favoring the three-dimensional bubble over the planar loop as a description of coronal mass motions.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 59
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    Propagation of energetic particles in the solar wind (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A summary is given of recent results from the direct determination of the charge states of He, C, O, and Fe. These results are used in discussing compositional variations during individual solar particle events. It is shown that ratio changes by a factor of approximately 10 during the onset phase of solar particle events can be explained not only by rigidity-dependent interplanetary propagation but also by rigidity-dependent diffusive propagation in the corona. Increasing experimental evidence is seen that other processes, such as compositional variations at the source and discontinuities of the interplanetary magnetic field separating two different particle populations, may be important. No common explanation is seen for all the variations, and it is concluded that each must be investigated on its own.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 60
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    Spatial variation for flares observed with the gamma ray spectrometer aboard the SMM satellite (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A search is made for anisotropic X-ray bremsstrahlung photon production from relativistic electrons by studying the heliocentric angular dependence of 53 flares detected at energies above 300 keV. No evidence is found for a higher rate of detectable flares near the limb at the 80 percent confidence level. This result implies that the X-ray directivity as defined by the ratio of photon intensity at 75 deg and 0 deg of heliocentric angle is less than 1.5 above 300 keV and strongly rejects any flare model predicting X-ray production from a radial 'beam' of energetic electrons.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 61
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    Some recent results in the interpretation of high brightness temperature microwave spike emission (1982)
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    Publication Date: 2019-06-28
    Description: A review is presented of theoretical work on the interpretation of short duration (1-100 msec), high brightness temperature (approximately 10 to the 15th K) spikes at microwave frequencies during the impulsive phase of some solar flares. Also examined is recent work on the interpretation of the spike emission as gyrosynchrotron masering. Two alternative radiation mechanisms, stimulated plasma emission from the coherent interaction of electrostatic upper hybrid waves and from the interaction of electron plasma waves, are examined.
    Keywords: SOLAR PHYSICS
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  • 62
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    Fluorescent excitation of photospheric Fe K-alpha emission during solar flares (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Bent Crystal Spectrometer on the NASA Solar Maximum Mission satellite provides high spectral and temporal resolution observations of the Fe K-alpha lines. Analyses have been conducted of spectra from almost 50 solar flares that occurred during 1980. These data strongly support fluorescent excitation of photospheric iron by photons of E greater than 7.11 keV emitted by the hot coronal plasma produced during the flare. After comparison of the data with a model, the observed K-alpha line widths are discussed along with estimates of the size of the emitting region, the height of the coronal source and the photospheric iron abundance.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 63
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    Direct evidence for chromospheric evaporation in a well-observed compact flare (1982)
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    Publication Date: 2019-06-28
    Description: Observations of the solar flare of May 7, 1980 using several Solar Maximum Mission instruments are presented as an investigation of the phenomenon of chromospheric evaporation. The total amount of plasma at temperatures greater than 2 x 10 to the 6th K were determined from the X-ray data, and the amount of plasma that was evaporated from the chromosphere was determined from the H-alpha data. The H-alpha profiles indicate that for the flare as a whole, at the time of peak soft X-ray emission measure, the number of atoms evaporated from the chromosphere was 7 x 10 to the 37th. The soft X-ray emission measure of 1 x 10 to the 49th/cu cm, coupled with the flare volume estimate of 10 to the 26th cu cm, indicates that there were 3 x 10 to the 37th electrons in the soft X-ray plasma with temperatures greater than 2 x 10 to the 6th K. These results indicate that enough material had been evaporated from the chromosphere to account for the X-ray plasma. Taken together, the H-alpha, soft X-ray, and hard X-ray images indicate that chromospheric evaporation is driven both by flare-accelerated electrons during the impulsive phase and by conduction during the thermal phase.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 64
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    Bright point study (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Transition region and coronal observations of bright points by instruments aboard the Solar Maximum Mission and high resolution photospheric magnetograph observations on September 11, 1980 are presented. A total of 31 bipolar ephemeral regions were found in the photosphere from birth in 9.3 hours of combined magnetograph observations from three observatories. Two of the three ephemeral regions present in the field of view of the Ultraviolet Spectrometer-Polarimeter were observed in the C IV 1548 line. The unobserved ephemeral region was determined to be the shortest-lived (2.5 hr) and lowest in magnetic flux density (13G) of the three regions. The Flat Crystal Spectrometer observed only low level signals in the O VIII 18.969 A line, which were not statistically significant to be positively identified with any of the 16 ephemeral regions detected in the photosphere. In addition, the data indicate that at any given time there lacked a one-to-one correspondence between observable bright points and photospheric ephemeral regions, while more ephemeral regions were observed than their counterparts in the transition region and the corona.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 65
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    The solar corona - A testing ground for plasma astrophysics (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The extension of solar surface activity models to the domain of stellar activity, and the possibility of testing such extensions, are discussed. The extrapolation of three canonical solar activity indicators, sunspots, Ca II emission, and solar flares, to other stars is considered. The use of satellites to study stellar activity at wavelengths at which surface activity is most prominent is briefly reviewed. The correlation of stellar activity with intrinsic stellar parameters, especially those relating to rotation, is briefly considered, and the use of phenomenological models of stellar coronal X-ray emission to deduce the magnetic flux production rate for observed stars as a function of rotation rate is discussed.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 66
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    The growth of filaments by the condensation of coronal arches (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A model of filament formation based on the condensation of coronal arches is described. The condensation results from initiating the radiative instability within an arch by superimposing a transient energy supply upon the steady state heating mechanism. The transient energy supply increases the density within the arch so that when it is removed the radiative losses are sufficient to lead to cooling below the minimum in the power loss curve. Times from the initial formation of the condensation to its temperature stabilization as a cool filament have been calculated for various initial conditions. They lie in the range 10,000-100,000 s with the majority of the time spent above a temperature of 1 x 10 to the 6th K. Under the assumption that the condensation of a single arch forms an element of the filament, a complete filament requires the condensation of an arcade of loops. Using experimentally derived parameters, filament densities of 10 to the 11th to 10 to the 12th per cu cm can be obtained.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 81; Dec. 198
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  • 67
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    A direct observation of solar neutrons following the 0118 UT flare on 1980 June 21 (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Gamma Ray Spectrometer on the Solar Maximum Mission satellite has observed energetic solar neutrons (greater than 50 MeV) at the earth following a solar flare that occurred on the west limb on June 21, 1980 at 01:18:20 UT. Impulsive photon emission from 10 keV to greater than 65 MeV lasting over a period of about 66 s was followed by a transient flux of 50-600 MeV neutrons incident over a 17 minute period. The peak counting rate corresponds to an average flux at the earth of (3.8 + or - 0.6) x 10 to the -2nd neutrons/sq cm s at 130 MeV. These observations indicate the emission of 3 x 10 to the 28th neutrons/sr with energies greater than 50 MeV, requiring the rapid acceleration (much less than 60 s) of protons to GeV energies during the impulsive phase of the flare.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 263
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  • 68
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    Solar radiometry - Spectral irradiance measurements (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The present measurement accuracy of the solar spectral irradiance is insufficient to derive the real long-term solar spectral irradiance variability at all wavelengths. Possible error sources are discussed. A series of new second generation solar irradiance photometers are now under construction which should considerably improve these measurements. At the same time, efforts are made to improve the absolute UV calibration methods to derive a unified UV radiation scale.
    Keywords: SOLAR PHYSICS
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  • 69
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    Structure of the heliospheric current sheet in the early portion of sunspot cycle 21 (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The structure of the heliospheric current sheet on a spherical source surface of radius 2.35 solar radii has been computed via the use of a potential field model during the first year and a half after the last sunspot minimum. The solar polar magnetic field that is not fully observed in conventional magnetograph scans was included in the computation. The computed heliospheric current sheet had a quasi-stationary structure consisting of two northward and two southward maxima in latitude per solar rotation. The extent in latitude slowly increased from about 15 deg near the start of the interval to about 45 deg near the end. The magnetic field polarity (away from the sun or toward the sun) at the subterrestrial latitude on the source surface agreed with the interplanetary magnetic field polarity observed or inferred at the earth on 82 percent of the days. The interplanetary field structure observed at the earth at this time is finely tuned to the structure of low-latitude fields on the source surface.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Dec. 1
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  • 70
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    Advances in solar radio astronomy (1982)
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    Publication Date: 2019-06-28
    Description: The status of the observations and interpretations of the sun's radio emission covering the entire radio spectrum from millimeter wavelengths to hectometer and kilometer wavelengths is reviewed. Emphasis is given to the progress made in solar radio physics as a result of recent advances in plasma and radiation theory. It is noted that the capability now exists of observing the sun with a spatial resolution of approximately a second of arc and a temporal resolution of about a millisecond at centimeter wavelengths and of obtaining fast multifrequency two-dimensional pictures of the sun at meter and decameter wavelengths. A summary is given of the properties of nonflaring active regions at millimeter, centimeter, and meter-decameter wavelengths. The properties of centimeter wave bursts are discussed in connection with the high spatial resolution observations. The observations of the preflare build-up of an active region are reviewed. High spatial resolution observations (a few seconds of arc to approximately 1 arcsec) are discussed, with particular attention given to the one- and two-dimensional maps of centimeter-wavelength burst sources.
    Keywords: SOLAR PHYSICS
    Type: Reports on Progress in Physics; 45; Dec. 198
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  • 71
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    A measurement of the magnetic field direction at the site of major flares (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Lundstedt et al. (1981) showed that the direction of the photospheric magnetic field at the site of a flare is a good predictor of the solar wind velocity observed at earth four days later. It is described here how the field direction was obtained, and possible errors involved in the determination of the angle are discussed. The discussion also includes a characterization of the solar active regions.
    Keywords: SOLAR PHYSICS
    Type: AD-A129819 , Solar Physics; 81; Dec. 198
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  • 72
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    High resolution EUV structure of the chromosphere-corona transition region above a sunspot (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Rocket observations are reported for a sunspot at high spatial and spectral resolution in the extreme ultraviolet region (EUV) between 1170 and 1715 A. The instrument and data reduction are described, and the appearance of the sunspot features in EUV emission lines is presented together with a correlation of the nonthermal velocity field with the Doppler velocity field. For sunspots the shape of the differential emission measure curve shows that the minimum is shifted to lower temperatures by over a factor of two, while the slope on a log-log scale near log of effective temperature equal to 5.3 is increased by a factor of two. This means that the energy balance is dominated by radiative losses from the large amount of transition region plasma, and an upper limit of a million K exists on the extrapolated temperature above the umbra. Static energy balance models of the umbra show that the observed enthalpy flux can balance radiative losses above 30,000 K for a fill factor greater than 0.1. An umbral model is compared with the chromospheric sunspot model of Kneer and Mattig (1978).
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 81; Dec. 198
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  • 73
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    Submillimeter extensions of the solar limb determined from observations of the total eclipse of 1981 July 31 (1982)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: First results are presented of observations of a lunar occultation of the solar limb made from the Kuiper Airborne Observatory in the 30 micrometr, 50 micrometer, 100 micrometer, and 200 micrometer continuum during the total solar eclipse of 1981 July 31. The solar limb was extended at the longer wavelengths up to 1000 km higher than predicted from smooth plane-parallel chromospheric models. Results at both second and third contact show the infrared limb extensions to be approximately 0".8, 1"5, 2".5 and 3".0 above the visible limb in the observed bands, respectively. A possible interpretation proposes chromospheric fine structure inhomogeneities of greater density than presently incorporated in models of the middle chromosphere.
    Keywords: SOLAR PHYSICS
    Type: NASA-TM-84306 , A-9154 , NAS 1.15:84306
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  • 74
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    The Pinhole/Occulter facility (1982)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The outer solar atmosphere exhibits a great variety of dynamic and energetic plasma phenomena, from the catastrophic energy release of solar flares to the steady acceleration of the solar wind. The Pinhole/Occulter Facility contains the instruments necessary for broadband X-ray imaging, combined with simultaneous ultraviolet and white light spectroscopy and imaging.
    Keywords: SOLAR PHYSICS
    Type: NASA-TP-2089 , NAS 1.60:2089
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  • 75
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    Unsteady, thermally conductive coronal flow (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A numerical algorithm using implicit time-differencing is applied to the solar wind equations allowing, for the first time, solutions including thermal conduction to be found for time-dependent flow traversing the subsonic to supersonic velocity transition region. Sample solutions are shown that demonstate the distinctive differences introduced by including thermal conduction, in comparison to the commonly available solutions assuming polytropic flow. Also, it is found that steady solutions are produced at least as quickly using a time-dependent relaxation to the steady state as when solving the steady-state equations.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 259
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  • 76
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    Formation of the O I resonance triplet and intercombination doublet in the solar chromosphere (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Spectrum synthesis calculations are presented for the O I resonance triplet at 1304 A and the intercombination doublet at 1358 A for the solar atmosphere and several variants, allowing for triplet fluorescence by the Ly-beta emission of H I. Profiles, synthesized from a seven-level plus continuum O I atom are compared to observations taken with the high-resolution spectrometer on OSO 8. It is found that the O I triplet emission is dominated by the Ly-beta fluorescence and that the agreement between observations and profiles computed with current chromospheric models is much improved over earlier studies.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 259
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  • 77
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    Whistler mode turbulence in the disturbed solar wind (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The magnetic field fluctuations with frequencies lying between the ion and electron cyclotron frequenices are enhanced downstream of interplanetary shocks in fast streams. Although spectra synthesized from ISEE 3 magnetometer and plasma wave instrument data can be described by one power law below 1 Hz, and another one above, measurement behind four shocks of the spectral index above the ion cyclotron frequency showed it to be twice the figure below, while no clear relationship is apparent in the weaker fast stream events. Although the data base is limited, the ratios of the average wave magnetic amplitude to electric field amplitudes confirm that the waves are whistler mode emissions, as suggested by their frequency range. It is indirectly deduced that the whistler waves are generated in such a way as to propagate at large angles to the local interplanetary field.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; Aug. 1
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  • 78
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    Radio wave heating of the corona and electron precipitation during flares (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Electron-cyclotron masers, excited while energy release is occurring in a flaring magnetic loop, are likely to generate extremely intense radiation at decimeter wavelengths. The energy in the radiation can be comparable with that in the electrons associated with hard X-ray bursts, i.e., a significant fraction of the total energy in the flare. Essentially all of the radio energy is likely to be reabsorbed by gyroresonance absorption, either near the emitting region or at some distance away in neighboring loops. Enhanced diffusion of fast electrons caused by the maser can lead to precipitation at the maximum possible rate, and hence account for hard X-ray emission from the footpoints of the magnetic loops.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 259
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  • 79
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    Umbral oscillations in a detailed model umbra (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Scheuer and Thomas (1981) theory of umbral oscillations as magneto-atmospheric wave resonant modes is extended and confirmed, by calculating the resonant modes of a more detailed model of the umbral atmosphere. The depths of forcing needed for the production of the 140-185 sec oscillation periods observed are in agreement with the depths of overstable convection found in such studies as that of Moore (1973) and Mullan and Yun (1973). The present study, along with those cited, offers a consistent explanation of umbral oscillations as a resonant response to oscillatory convection in the umbral subphotosphere. The response is in the form of a trapped, fast, magneto-atmospheric wave in the photosphere and chromosphere.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 79; July 198
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  • 80
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    An association between coronal structures and type III burst sources (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations of the coronal structures overlying type III radio burst producing regions, obtained with the HAO Coronograph/Polarimeter on board the Solar Maximum Mission, have been combined with observations of the type III bursts from the Mark III Nancay Radioheliograph at 169 MHz. A first qualitative comparison of the data, performed for two periods, indicates that the corona overlying type III producing sites is composed of small, discrete, over-dense structures, which are sometimes diverging and short-lived. The type III burst sources are complex, exhibiting elementary components. It is suggested that the type III burst structure follows that of the corona and that discrete structures may play a fundamental role for type III production.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 111; 2, Ju; July 198
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  • 81
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    A magnetohydrodynamic theory of coronal loop transients (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The physical and geometrical characteristics of solar coronal loop transients are described in an MHD model based on Archimedes' MHD buoyancy force. The theory was developed from interpretation of coronagraphic data, particularly from Skylab. The brightness of a loop is taken to indicate the electron density, and successive pictures reveal the electron enhancement in different columns. The forces which lift the loop off the sun surface are analyzed as an MHD buoyancy force affecting every mass element by imparting an inertial force necessary for heliocentrifugal motion. Thermal forces are responsible for transferring the ambient stress to the interior of the loop to begin the process. The kinematic and hydrostatic buoyancy overcome the gravitational force, and a flux rope can then curve upward, spiralling like a corkscrew with varying cross section around the unwinding solar magnetic field lines.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 78; June 198
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  • 82
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    Beam-plasma instability in the presence of low-frequency turbulence (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: General equations are derived for a linear beam-plasma instability in the presence of low-frequency turbulence. Within a 'quasi-linear' statistical approximation, these equations contain Langmuir wave scattering, diffusion, resonant and nonresonant anomalous absorption, and a 'plasma laser' effect. It is proposed that naturally occurring density irregularities in the solar wind may stabilize the beam-unstable Langmuir waves which occur during type III solar emissions.
    Keywords: SOLAR PHYSICS
    Type: Physics of Fluids; 25; June 198
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  • 83
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    Impulsive phase of flares in soft X-ray emission (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations using the bent crystal spectrometer instrument on the Solar Maximum Mission show that turbulence and blue-shifted motions are characteristic of the soft X-ray plasma during the impulsive phase of flares, and are coincident with the hard X-ray bursts observed by the hard X-ray burst spectrometer. A method for analysing the Ca XIX and Fe XXV spectra characteristic of the impulsive phase is presented. Nonthermal widths and blue-shifted components in the spectral lines of Ca XIX and Fe XXV indicate the presence of turbulent velocities exceeding 100 km/s and upward motions of 300-400 km/s. The April 10, May 9, and June 29, 1980 flares are studied. The April 10 flare has two separated footpoints bright in hard X-rays. Plasma heated to temperatures greater than ten million K rises from the footpoints. During the three minutes in which the evaporation process occurs an energy of 3.7 x 10 to the 30th ergs. This is consistent with the above figures, allowing for loss by radiation and conduction.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 78; May 1982
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  • 84
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    A model of a sunspot chromosphere based on OSO 8 observations (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: OSO 8 spectrometer observations of the H I, Mg II, and Ca II resonance lines of a large quiet sunspot during November 16-17, 1975, along with a C IV line of that event obtained by a ground-based spectrometer, are analyzed together with near-simultaneous ground-based Stokes measurements to yield an umbral chromosphere and transition region model. Features of this model include a chromosphere that is effectively thin in the resonance lines of H I and Mg II, while being saturated in Ca II, and an upper chromospheric structure similar to that of quiet-sun models. The similarity of the upper chromosphere of the sunspot umbra to the quiet-sun chromosphere suggests that the intense magnetic field plays only a passive role in the chromospheric heating mechanism, and the observations cited indicate that solar-type stars with large areas of ordered magnetic flux would not necessarily exhibit extremely active chromosphere.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal Supplement Series; 49; June 198
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  • 85
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    An analysis of shock wave disturbances observed at 1 AU from 1971 through 1978 (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: IMP 6, 7, and 8 data from 104 shock wave disturbances were employed to document the occurrence frequency and properties of the solar wind shock which produce He ion abundance enhancements. The shocks were identified over the 1971-1978 time period and were characterized by a preshock flow with lower than usual average bulk density, a shocked gas layer 12 hr thick, and a postshocked gas layer 1.5 days thick with a high He abundance. A high-temperature peak was found to occur in the first 12 hrs after a He-enriched shock and was not seen when He-enhancement was absent. The total pressure was also three times higher with He-shocks, and speed jumps were greater than 50 km/sec in 56% of the He events. It is concluded that all shock waves in the solar wind at 1 AU originate in coronal mass ejection events, and the presence of He-enrichment is attributable to the geometry of the area that produced the event.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; June 1
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  • 86
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    A study of solar flare soft X rays and their relation to particle events observed with IMP 8 (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Data from the Johns Hopkins University Applied Physics Laboratory charged particle measurement experiment aboard IMP 8 was used to study solar flare events and find correlations between soft X rays (4-17 A) and particle events. The results show that a greater probability exists of observing a proton event if the observed soft X ray flare has a relatively large decay time. It is also found that the H-alpha brightening area is a good indicator of the strength of the soft X ray burst. Results also show that the strength of the soft X ray burst can be used to estimate a probability that a proton event will occur, along with the strength of that particle event.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 87; June 1
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  • 87
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    Observation of additional low-degree 5-min modes of solar oscillation (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: High-order solar oscillations with degrees l=3, 4, and 5 could be detected. The observations were made by measuring the difference between the shifts in the Fe 5,124 spectrum line from light integrated from a central circular portion of the solar disk and from an annular portion exterior to it. The frequencies of the octupole modes agree well with the values obtained from whole-disk measurements at the South Pole. A least-squares fit of the observed frequencies to values interpolated between and extrapolated from the predictions of a sequence of solar models with different chemical compositions selects two models. One, a helium-rich solution, agrees with that of similar analyses of whole-disk data. The extrapolated solution has a relatively deep convection zone, and is thus consistent with analyses of 5-min oscillations of high degree.
    Keywords: SOLAR PHYSICS
    Type: Nature; 297; May 27
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  • 88
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    On the origin of solar spicules (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The nonlinear evolution of vertical motions on intense solar magnetic flux tubes is considered. It is shown that a quasi-impulsive source in the photosphere can excite a train of upward-propagating rebound shocks in the chromosphere. The rebound shock train is the nonlinear development of oscillations of the atmosphere at its natural frequency. The rebound shocks impinge on the transition region and thrust the underlying chromosphere upward. It is found that the rebound shock train leads naturally to structures which can be identified with the solar spicules.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 257
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  • 89
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    Electron pitch angle scattering and the impulsive phase microwave and hard X-ray emission from solar flares (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations and theoretical considerations have led to a model for impulsive phase flare emission involving the heating and acceleration of thermal electrons in the coronal part of a magnetic loop. The bulk of the heated gas is confined between conduction fronts, but particles with velocities a few times greater than the thermal velocity can escape into the lower part of the loop. It is shown that, when the electron gyrofrequency exceeds the plasma frequency, the escaping electrons are unstable to the generation of electrostatic plasma waves which scatter the particles in pitch angle to a nearly isotropic distribution. It is also shown that this scattering can (1) enhance the microwave emission from the upper part of the loop, and (2) due to the Landau damping of both low and high phase velocity waves, can lead to one or two breaks in the impulsive-phase hard X-ray spectrum.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 257
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  • 90
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    A mechanism for a class of solar coronal disturbances (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A new ideal magnetohydrodynamic (MHD) model is used to examine the dynamical response of the upper solar atmosphere to the injection of cold mass from the photosphere, a surge perturbation. Theoretical results show that mass ejections from the photosphere will form loop structures with internally-moving plasma blobs, which is due to the mass injections from both legs in active regions leading to a reflection of waves at the top of the loop. The mass-loaded loop will remain as long as ejection continues, and will excite MHD waves propagating outward to the upper atmosphere, which may trigger a class of coronal disturbances.
    Keywords: SOLAR PHYSICS
    Type: Astrophysics and Space Science; 83; 1-2,; Apr. 198
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  • 91
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    Impulsive and gradual hard X-ray sources in a solar flare (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The paper reports recent observations of a relatively large hard X-ray burst with well developed impulsive and gradual components, that was associated with a relatively modest optical flare on Aug. 14, 1979. The impulsive X-ray source has a much higher ion density and the electron injection in the phase is shorter in duration consisting of fewer energetic electrons than in the gradual phase. The gradual X-ray source seems to consist of a lower density region, probably bounded by a magnetic arch in which the energetic electrons are perfectly trapped. The different temporal development of the impulsive and gradual hard X-ray components suggest large differences in the physical parameters of the ambient plasma.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 108; 2, Ap; Apr. 198
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  • 92
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    Solar flare X-ray spectra from the Solar Maximum Mission Flat Crystal Spectrometer (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: High-resolution solar X-ray spectra obtained with the Flat Crystal Spectrometer aboard the Solar Maximum Mission from two solar flares and a nonflaring active region are analyzed. The 1-22 A region was observed during the flare on 1980 August 25, while smaller spectral regions were repeatedly covered during the 1980 November 5 flare. Voigt profiles were fitted to spectral lines to derive accurate wavelengths and to resolve blends. During the August 25 flare, 205 lines were found in the range 5.68-18.97 A, identifications being provided for all but 40 (mostly weak) lines. Upper limits to flare densities are derived from various line ratios, the hotter (about 10 to the 7th K) ions giving an electron density of less than 10 to the 12th per cu cm for the August 25 flare. Other observed line ratios (e.g., in Fe XVII and Mg XII) indicate a need for revisions in theoretical calculations.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 256
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  • 93
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    Solar flares, proton showers, and the Space Shuttle (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Attention is given the hazards posed to Space Shuttle crews by energetic proton radiation from inherently unpredictable solar flares, such as that of April 10-13, 1981, which was experienced by the Space Shuttle Columbia. The most energetic protons from this flare reached the earth's atmosphere an hour after flare onset, and would have posed a potentially lethal threat to astronauts engaged in extravehicular activity in a polar or geosynchronous orbit rather than the low-latitude, low-altitude orbit of this mission. It is shown that proton-producing flares are associated with energization in shocks, many of which are driven by coronal mass ejections. Insights gained from the Solar Maximum Year programs allow reconsideration of proton shower forecasting, which will be essential in the prediction of the weather that Space Shuttle astronauts will encounter during extravehicular activities.
    Keywords: SOLAR PHYSICS
    Type: Science; 216; May 28
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  • 94
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    Identification of Fe I lines in the ultraviolet solar spectrum (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: High-resolution ultraviolet echelle spectrograms of the sun obtained from a rocket-borne spectrograph have been used for the identification of Fe I absorption lines in the wavelength range 1770-2020 A. Wavelength measurements, with a precision of about 15 mA, are tabulated for 425 Fe I features, along with available laboratory wavelenghs or predicted wavelengths calculated from atomic energy level data. The classification system of Moore has been extended to include possible additional multiplets with 126 newly classified lines; 234 unclassified lines were observed and identified with laboratory Fe I spectra
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal Supplement Series; 48; Apr. 198
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  • 95
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    The evolution of solar ultraviolet luminosity (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Astronomical observations of stars analogous to the sun are used to construct a tentative account of the evolution of solar UV luminosity. Evidence exists that the young sun was a much more powerful source of energetic particles and radiation than it is today, and while on the main sequence, solar activity has declined as an inverse power law of age as a consequence of angular momentum loss to the solar wind. Observations of pre-main sequence stars indicate that before the sun reached the main sequence, it may have emitted as much as ten thousand times the amount of ultraviolet radiation that it does today. The impact of the results on knowledge of photochemistry and escape of constituents of primordial planetary atmospheres is discussed.
    Keywords: SOLAR PHYSICS
    Type: Reviews of Geophysics and Space Physics; 20; May 1982
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  • 96
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    Simulation of the magnetic structure of the inner heliosphere by means of a non-spherical source surface (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: (Previously announced in STAR as N81-18977)
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 77; Apr. 198
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  • 97
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    Evidence of redshifts in the average solar line profiles of C IV and Si IV from OSO-8 observations (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Line profiles of C IV and Si V obtained by the Colorado spectrometer on OSO-8 are presented. It is shown that the mean profiles are redshifted with a magnitude varying from 6-20 km/s, and with a mean of 12 km/s. An apparent average downflow of material in the 50,000-100,000 K temperature range is measured. The redshifts are observed in the line center positions of spatially and temporally averaged profiles and are measured either relative to chromospheric Si I lines or from a comparison of sun center and limb profiles. The observations of 6-20 km/s redshifts place constraints on the mechanisms that dominate EUV line emission since it requires a strong weighting of the emission in regions of downward moving material, and since there is little evidence for corresponding upward moving materials in these lines.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 77; Apr. 198
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  • 98
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    Remote flare brightenings and type III reverse slope bursts (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations are presented on two large (H-alpha class 2) flares that each produced an extensive chain of discrete H-alpha brightenings spanning 370,000-470,000 km in length in remote quiet regions more than 100,000 km from the main flare site. A large group of Type III RS bursts was also observed accompanying each flare. The onset of about half the remote H-alpha emission patches were nearly simultaneous with the RS bursts. One flare was observed in hard X-rays, and it is noted that the RS bursts occurred during hard X-ray spikes. For the other flare, soft X-ray filtergrams indicate coronal loops connecting from the main flare site to the remote H-alpha brightenings. Observations indicate that the RS burst electrons were generated in the flares, and it is proposed that the remote H-alpha brightenings were initiated by direct heating of the chromosphere by RS burst electrons traveling in closed magnetic loops connecting the flare site to the remote patches. It is also suggested that after onset, the brightenings were heated by thermal conduction by slower thermal electrons.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 77; Apr. 198
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  • 99
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    Positions of type II fundamental and harmonic sources in the 30-100 MHZ range (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An excellent example of a type III-V burst followed by a type II burst with fundamental and harmonic bands was observed on June 18, 1979 at the Clark Lake Radio Observatory. The observations are described in detail and their implications are discussed with regard to the problem of directionality with respect to the magnetic field lines of the collisionless MHD shock wave generated at the start of the flash phase. It is found that the positions of type III and type II (F) bursts at a number of frequencies are essentially the same, which implies that the shock responsible for the type II radiation follows the path of the type III exciter, that is, the shock propagates along the open field lines.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 77; Apr. 198
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  • 100
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    The role of betatron acceleration in complex solar bursts (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An explanation in terms of betatron acceleration is attempted for two prominent features of solar hard X-ray emission profiles: the multiplicity manifested by complex impulsive events, and the intense, long-enduring radiation typical of two-stage or extended events. The model employs the basic characteristics of a simple magnetic trap. The observed spectral evolution can be represented effectively by a set of characteristics derived in a thick-target representation. The application to multiple-spike and two-stage bursts is studied, and it is found that impulsive events show no signs of betatron acceleration. However, during the first few minutes of the second stage, the nonimpulsive X-ray emission appears to be consistent with the predictions of the model. Several intense extended events are analyzed and the betatron process is established as a viable candidate for producing the early second-stage emission.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 77; Apr. 198
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