DIRECTIONALITY OF SOLAR FLARE-ACCELERATED PROTONS AND α-PARTICLES FROM γ-RAY LINE MEASUREMENTS

摘要

The energies and widths of γ-ray lines emitted by ambient nuclei excited by flare-accelerated protons and α-particles provide information on the ions' directionality and spectra and on the characteristics of the interaction region. We have measured the energies and widths of strong lines from de-excitations of ~(12)C, ~(16)O, and ~(20)Ne in solar flares as a function of the heliocentric angle. The line energies from all three nuclei exhibit ～1% redshifts for flares at small heliocentric angles but are not shifted near the limb. The lines have widths of ～3% FWHM. We compare the ~(12)C line measurements for flares at five different heliocentric angles with calculations for different interacting-particle distributions. A downward isotropic distribution (or one with a small upward component) provides a good fit to the line measurements. An angular distribution derived for particles that undergo significant pitch-angle scattering by MHD turbulence in coronal magnetic loops provides comparably good fits.