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Session 26 - Solar Flares II.
Oral session, Monday, June 10
Wisconsin Center,

[26.05] Measurement of Ion Anisotropy in Flares Using Gamma-Ray Lines

G. H. Share, R. J. Murphy (NRL)

The line profiles of ^7Be and ^7Li produced by interactions of flare- accelerated \alpha-particles with ambient He are sensitive to the angular distributions of the \alpha-particles (Kozlovsky and Ramaty, 1977). Murphy et al. (1988, 1990) have calculated the profiles expected for a variety of angular distributions both at the solar limb and at its center. They also demonstrated that instruments with the moderate resolution achieved by NaI detectors, such as the Gamma Ray Spectrometer (GRS) on the Solar Maximum Mission satellite, can provide information on the angular distributions. Their investigation of the spectrum observed from the 1981 April 27 flare showed that characteristic angular distributions occurring at the limb could be distinguished from those at disk center. In this paper we extend this study to 19 flares observed by the GRS which had significant nuclear line emission (Share and Murphy, 1995). We fit the spectra from 0.35 to 0.75 MeV with models containing electron bremsstrahlung, the 511 keV annihilation line and positronium continuum (or Compton scattered continuum), and various \alpha-\alpha line profiles. Some of these flares occurred closer to disk center, where it may be possible to determine whether the accelerated particles were isotropically distributed or beamed. This work was supported by NASA under contract DPR W-18323.

Program listing for Monday