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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[18.06] Characterization of the RHESSI 3-10 keV spectrum

H.S. Hudson (UCB), B.R. Dennis, K.J.H. Phillips, R.A. Schwartz (NASA/GSFC), D.M. Smith (UCB)

We describe an empirical characterization of the RHESSI X-ray spectrum in the 3-10 keV range, using a sample of flares for which the attenuating shutters remained open. The main spectral features comprise the continuum, which we study in two broad-band ranges (F3: 2.83-5.5 keV, and F8: 7.5-10.17 keV). The lower-energy band F3 normally shows time profiles resembling those of the GOES hard channel, and the F8/F3 ratio exhibits a heating/cooling variation similar to that of the two GOES channels; in addition an impulsive component appears in the F8 channel. In between these bands lies the prominent Fe line complex. We fit the Fe excess emission to a Gaussian, using 2-sec integrations, and find values of sigma on the order of 0.3-0.4 keV for most of the RHESSI detectors. This emission feature embraces the 2-1 transitions for all of the Fe ionization states. The centroid of the Fe line feature varies significantly in energy as the flare evolves; the time variability resembles the F8 continuum more than the F3 continuum. We present statistical results for these properties of the 3-10 keV spectrum, including the systematic variation of Fe feature equivalent width.

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