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  • 21
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    Thermal bifurcation in the upper solar photosphere inferred from heterodyne spectroscopy of OH rotational lines (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Low noise high spectral resolution observations of two pure rotation transitions of OH from the solar photosphere were obtained. The observations were obtained using the technique of optically null-balanced infrared heterodyne spectroscopy, and consist of center-to-limb line profiles of a v=1 and a v=0 transition near 12 microns. These lines should be formed in local thermodynamic equilibrium (LTE), and are diagnostics of the thermal structure of the upper photosphere. The v=0 R22 (24.5)e line strengthens at the solar limb, in contradiction to the predictions of current one dimensional photospheric models. Data for this line support a two dimensional model in which horizontal thermal fluctuations of order + or - 800K occur in the region Tau (sub 5000) approximately .001 to .01. This thermal bifurcation may be maintained by the presence of magnetic flux tubes, and may be related to the solar limb extensions observed in the 30 to 200 micron region.
    Keywords: SOLAR PHYSICS
    Type: NASA-TM-86128 , NAS 1.15:86128
    Format: application/pdf
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  • 22
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    Associations between coronal mass ejections and solar energetic proton events (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A comparison between proton events and coronal mass ejections (CMEs) based on nearly three years of observations around the recent maximum of solar activity is presented. Peak proton fluxes are found to correlate with both the speeds and the angular sizes of the associated CMEs. It is shown that CME speeds do not significantly correlate with CME angular sizes, so that peak proton fluxes are correlated with two independent CME parameters. With larger angular sizes, CMEs are more likely to be loops and fans rather than jets and spikes and are more likely to intersect the ecliptic.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 9683-969
    Format: text
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  • 23
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    Large loop thermal models of solar hard X-ray bursts (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results for small loop thermal models of hard X-ray bursts are extended to large loops. In this model a magnetic arch with a coronal length of 45,000 km has the electrons near the top heated to temperatures above 1 billion K. The resulting conduction fronts which form are dominated by collisionless processes and travel down the arch to the transition region and chromosphere where they evaporate off part of the latter. This relatively cool material travels back up the loop and eventually quenches the source for energy injection times of order 10 sec. Most of the X-ray emission comes from the footpoints of the arch over most of the source lifetime and the spectrum is a power law with a typical spectral index of 3.0. Even though the efficiency gain in this model is only 2.8, it is much easier from the point of view of plasma physics to heat all the electrons in a plasma than to accelerate a substantial fraction of them.
    Keywords: SOLAR PHYSICS
    Type: ESA Plasma Astrophys.; p 401-404
    Format: text
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  • 24
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    Eclipse radius measurements (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Methods for predicting the path edges and reducing observations of total solar eclipses for determining variations of the solar radius are described. Analyzed observations of the 1925 January eclipse show a 0.7 (arc second) decrease in the solar radius during the past fifty years.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 117-120
    Format: application/pdf
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  • 25
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    Associations between coronal mass ejections and metric type II bursts (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A statistical comparison of metric type II bursts and coronal mass ejections (CMEs) during 1979-1982 was carried out. Type II bursts without CMEs were associated with short-lived (0.5 hr) soft X-ray events, but not with interplanetary shocks at the Helios 1 spacecraft. Type II bursts with CMEs were associated with longer-lived X-ray events (3 hr on the average) and interplanetary shocks, and the CMEs had speeds greater than 400 km/s. CMEs without metric type II bursts were divided equally into groups faster and slower than 455 km/s. The faster CMEs were associated with interplanetary shocks, some of which originated on the visible disk where metric type II bursts should have been observed if they had occurred. These results suggest that (1) shocks without CMEs have a relatively impulsive origin and may die out sooner than many shocks with CMEs which are piston driven, and (2) either some fast CMEs do not reach shock-producing super-Alfvenic speeds until they leave the lower corona where the metric emission originates, or these CMEs form shocks that are unable to excite type II emission in the lower corona.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 279; 839-847
    Format: text
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  • 26
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    The corona near the time of the 1983 June 11 total solar eclipse (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations are presented of the corona during the June 11, 1983 total solar eclipse, together with preliminary results of a coordinated observing program conducted to investigate the relationship between the corona and the lower parts of the solar atmosphere. Synoptic observations of the white light corona and disk in H-alpha are compared with the eclipse image, together with the inferred longitudinal component of the photospheric magnetic field measured using the magnetically sensitive Fe line at 6303 A. Using these data, an interpretation of the global three-dimensional coronal structure is attempted; showing that the eclipse image contains bright features which are far from the plane of the sky, and that it is dominated by streamers over polar filament neutral lines.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 278; L123-L12
    Format: text
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  • 27
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    Determination of variations of the solar radius from solar eclipse observations (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper describes the method to determine the solar radius and its variations from observations made during total solar eclipses. In particular, the procedure to correct the spherical moon predictions for the effects of lunar mountains and valleys on the width and location of the path of totality is addressed in detail. The errors affecting this technique are addressed, a summary of the results of its application to three solar eclipses are presented, and the implications of the results on the constancy of the solar constant are described.
    Keywords: SOLAR PHYSICS
    Type: Conference on The ancient sun: Fossil record in the earth, moon and meteorites; Oct 16, 1979 - Oct 19, 1979; Boulder, CO
    Format: text
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  • 28
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    The Lockheed OSO-8 program. Analysis of data from the mapping X-ray heliometer experiment (1980)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The final report describes the extent of the analysis effort, and other activities associated with the preservation and documentation of the data set are described. The main scientific results, which are related to the behavior of individual solar activity regions in the energy band 1.5 - 15 keV, are summarized, and a complete bibliography of publications and presentations is given. Copies of key articles are also provided.
    Keywords: SOLAR PHYSICS
    Type: NASA-CR-160087 , LMSC-D766866
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  • 29
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    The sunspot chromosphere-corona transition region (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Data from simultaneous readings of the line intensities, Doppler shifts, and line widths of a sunspot ion emission lines between 1170-1700 A are reported. Subsonic and supersonic flows were observed in the same line of sight above the umbra. A reduction of coronal plasma over sunspots with an electron temperature exceeding 1,000,000 K was confirmed, concurrent with enhanced emission from the transition region plasma in the temperature range 200,000-1,000,000 K. The differential emission measure is noted to have been caused to shift because of the enhancement of the transition region plasma emission, where radiative losses dominated the energy balance. Calculations of the energy balance also indicated that a detected divergence in the enthalpy flux for the umbral downflows could balance the radiative losses in the electron temperature range 30,000-200,000 K.
    Keywords: SOLAR PHYSICS
    Type: The physics of sunspots; Conference; Jul 14, 1981 - Jul 17, 1981; Sunspot, NM
    Format: text
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  • 30
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    Energetic electrons and plasma waves associated with a solar type III radio burst (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Detailed in situ observations from the ISEE 3 spacecraft of energetic electrons, plasma waves, and radio emission for the type II solar radio burst of February 17, 1979, are presented. The reduced, one-dimensional electron distribution function is constructed as a function of time. Since the faster electrons arrive before the slower ones, a bump on tail distribution forms which is unstable to the growth of Langmuir waves. The plasma wave growth computed from the distribution function agrees well with the observed onset of the Langmuir waves, and there is qualitative agreement between variations in the plasma wave levels and in the development of regions of positive slope in the function. The evolution of the function, however, predicts far higher plasma wave levels than those observed. The maximum levels observed are approximately equal to the threshold for nonlinear wave processes, such as oscillation two-stream instability and soliton collapse.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 251
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