HR: 09:30h
AN: SP41C-05    [Abstracts]
TI: Distinguishing between thermal and non-thermal electron populations in solar flares using RHESSI
AU: * Caspi, A
EM: cepheid@ssl.berkeley.edu
AF: Department of Physics and Space Sciences Laboratory, University of California, Berkeley, CA 94720 United States
AU: Lin, R P
EM: rlin@ssl.berkeley.edu
AF: Department of Physics and Space Sciences Laboratory, University of California, Berkeley, CA 94720 United States
AB: Solar flare plasmas contain thermal and non-thermal electron populations, both of which emit characteristic X-ray bremsstrahlung spectra. The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observes X-rays above 3~keV with a spectral resolution of ~1~keV FWHM. RHESSI spectra typically show a thermal continuum dominant below ~10~keV and a non-thermal continuum dominant above ~30~keV. Distinguishing between the two electron populations is crucial in determining the total energy contained in non-thermal electrons. High-temperature plasmas also emit characteristic line spectra, including emission in the Fe and Fe/Ni "line complexes" at ~6.7 and ~8~keV. Recent predictions and subsequent empirical confirmation have shown that the fluxes and equivalent widths of these complexes are strongly temperature-dependent (Phillips 2004, Caspi et al. 2004). We use the Fe and Fe/Ni line complexes to obtain constraints on the thermal electrons for a variety of large (GOES class M and X) solar flares, with emphasis on the X4.8 event on 23 July 2002, to determine the time-varying characteristics of the thermal and non-thermal electron populations. We estimate and compare the energy contained in these electrons, and discuss the implications for acceleration and heating of electrons in solar flares.
UR: http://sprg.ssl.berkeley.edu/~cepheid/agu_spd2005
DE: 7514 Energetic particles (2114)
DE: 7519 Flares
DE: 7554 X rays, gamma rays, and neutrinos
DE: 7594 Instruments and techniques
SC: Solar Physics Division - AAS [SP]
MN: 2005 Joint Assembly