A Survey of Solar Flare Energetic Particle Abundances and Energy Spectra.
Abstract
Previous surveys of the relative abundances of energetic particles accelerated in large solar flare events averaged the ionic composition in a single, summary energy interval. This study presents the time-integrated energy spectra of H, He, O, and Fe measured in ten large flare events observed at 1 AU over the energy range of ~0.3-80 MeV/Nucleon. Combined measurements from the University of Maryland/Max Planck Institute sensors on the ISEE-1 spacecraft and Goddard Space Flight Center instrumentation on IMP-8 extended the energy range beyond that measured with any single instrument of this study. The spectra showed consistent patterns in the abundances relative to oxygen and helium as functions of energy: particles with larger mean charge-to-mass ratios were generally less abundant at higher energies. In contrast to previous surveys made near 1 MeV/Nucleon and near 10 MeV/Nucleon, we found that these trends with energy remained in an average across many events. We compared abundances integrated over 0.3 -100 MeV/Nucleon and 4.94-22.5 MeV/Nucleon with other solar system abundances: the lower energy flare composition was more similar to the solar wind composition and showed a factor of 4 enrichment in Fe/O compared to the photospheric abundances. A model of stochastic particle acceleration with rigidity dependent diffusion coefficients gave the best overall fits to the energy spectra, a quantitative explanation of the observed energy dependences of the abundances, and a means of interpolating small portions of the energy spectra which the instrumentation did not measure.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1991
- Bibcode:
- 1991PhDT........14M
- Keywords:
-
- Physics: Astronomy and Astrophysics;
- Energetic Particles;
- Energy Spectra;
- Explorer 50 Satellite;
- International Sun Earth Explorer 1;
- Particle Energy;
- Solar Flares;
- Diffusion Coefficient;
- Particle Acceleration;
- Photosphere;
- Solar System;
- Solar Wind;
- Stochastic Processes;
- Solar Physics