34th Solar Physics Division Meeting, June 2003
Session 18 RHESSI Results II
Poster, Wednesday, June 18, 2003, 3:30-5:00pm, Mezzanine

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[18.09] Thermal and Nonthermal Contributions to the Flare X-ray Flux

B. R. Dennis, K. J. H. Phillips (NASA Goddard Space Flight Center), R. A. Schwartz, A. K. Tolbert (SSAI & NASA Goddard Space Flight Center), H. S. Hudson (U. Cal. Berkeley), RHESSI Team

The relative thermal and nonthermal contributions to the total flare energy budget are being determined through analysis of RHESSI imaging and spectroscopy X-ray observations in the critical energy range from a few keV to a few tens of keV. The classic ways of differentiating between the thermal and nonthermal components – exponential vs. power-law spectra, impulsive vs. gradually varying flux, compact vs. extended sources – can now be combined together for individual flares. In addition, RHESSI’s sensitivity and fine energy resolution of ~1 keV FWHM allow the intensity and mean energy of the iron-line complex between 6 and 7 keV to be measured as a function of time. Thus, the temperature and emission measure of the thermal plasma can be determined in a consistent manner assuming only the abundance of iron and the thermal origin of the emission. This then defines the thermal continuum spectrum and allows it to be cleanly separated from any nonthermal component that may be required to fit the measured spectrum at higher energies. Examples of such separations of the thermal and nonthermal components will be presented for several flares. The intensity of the iron line complex is consistent with an iron abundance equal to the solar coronal abundance as given by Feldman (1992), i.e., three times higher than the photospheric abundance

The author(s) of this abstract have provided an email address for comments about the abstract: Brian.R.Dennis@nasa.gov

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.