HR: 1330h
AN: SH22A-0170    [PDF]
TI: RHESSI Observations of High-Temperature Plasmas in Solar Flares
AU: * Caspi, A
EM: cepheid@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 United States
AU: * Caspi, A
EM: cepheid@ssl.berkeley.edu
AF: Department of Physics, University of California, Berkeley, CA 94720-7300 United States
AU: Krucker, S
EM: krucker@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 United States
AU: Lin, R P
EM: rlin@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 United States
AU: Lin, R P
EM: rlin@ssl.berkeley.edu
AF: Department of Physics, University of California, Berkeley, CA 94720-7300 United States
AB: Solar flare plasmas are multi-thermal, and in particular may contain high-temperature components above $\sim$20 MK. While other solar instruments (e.g. TRACE, GOES SXI) are sensitive to low-temperature plasmas below $\sim$20 MK, the {\it Reuven Ramaty High Energy Solar Spectroscopic Imager} (RHESSI) observes photons with energies above 3 keV, and thus is especially sensitive to high-temperature plasmas above $\sim$10 MK. High-temperature plasma emission includes the Fe/Ni line complexes at $\sim$6.7 and $\sim$8 keV, and both the equivalent widths and the fluxes of these line complexes are strongly temperature-dependent. In many flares, RHESSI detects emission in both of these line complexes, as well as emission in the thermal continuum, with spectral resolution of $\sim$1 keV FWHM. Through imaging and spectroscopy with RHESSI, and by comparison with other solar instruments, we can thus constrain the temperatures and emission measures over the entire range of thermal plasmas. We present a spectroscopic analysis of a variety of flares, including the X1.5 event on 21 April 2002, to determine the time-varying characteristics of the thermal electron populations. We estimate the energy contained in thermal electrons and compare with the energy contained in the time-varying non-thermal electron population. Finally, we discuss the implications for heating and energy transport in flares with high-temperature components.
UR: http://sprg.ssl.berkeley.edu/~cepheid/agu2003
DE: 7519 Flares
DE: 7554 X rays, gamma rays, and neutrinos
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting