Other
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sp42a07a&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #SP42A-07
Other
7519 Flares, 7554 X Rays, Gamma Rays, And Neutrinos
Scientific paper
This dissertation work expands the current understanding of the 15 November 1991 X 1.5 solar flare. This flare was a well observed event in radio to gamma-ray energies and is the first gamma-ray flare to be extensively studied with the benefit of detailed soft and hard X-ray images. In this work, we add data from all four instruments on the Compton Gamma Ray Observatory (CGRO), spanning 20 keV - 300 MeV. From these data we determined that the accelerated electron spectrum above 170 keV is best fit with a power law of spectral index γ ~-4.6. We determined that the accelerated proton spectrum above 0.6 MeV is also fit with a power law, with spectral index s ~-4.5. From these distributions, we computed a lower limit for the energy content of these particles: ~1023 ergs for the electrons above 170 keV and ~1027 ergs for the ions above 0.6 MeV. These particles do not have enough energy to produce the white light emission observed from this event. We compute a time constant τ of 26 (+20, -15) s for the 2.223 MeV neutron capture line. This is consistent at the 2σ level with the lowest values of ~70 s found for other flares. We modeled the impulsive X-ray emission from this flare with a 1D spatial diffusion equation (Ryan and Lee, 1991). We assumed a constant magnetic field and that turbulence and collisions affect the transport of particles. For relativistic electrons, we found that X-ray observations during the impulsive phase can be explained if turbulence is present such that the mean free path between interactions is 0.1 % of the total loop length. Collisions can be included, but are not necessary. We found that the injection source of accelerated particles is most likely located near the apex of the coronal loop. This model can also explain other features of the X-ray observations.
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