Spectral Analysis and Energy Estimates in M/X Flares using RHESSI and SXI Amir Caspi 1,2, Säm Krucker 2, Robert P. Lin 1,2 1 Department of Physics, University of California, Berkeley, CA Space Sciences Laboratory, University of California, Berkeley, CA 94720

June 19, 2003AAS/SPD Meeting2 Why is spectral analysis important? Provides estimates of energy in thermal and non-thermal electrons Provides clues to heating mechanism(s) How does SXI help? –Broad band response in soft X-rays –Sensitive to lower-temperature plasmas –Another estimate of thermal energy

June 19, 2003AAS/SPD Meeting3 01/24/2003 M1.9 flare

June 19, 2003AAS/SPD Meeting4 Fitting the spectra Forward modeling - which model/fit is best/proper?

June 19, 2003AAS/SPD Meeting5 Thermal + Power Law - Naïve model, poor fit early on, requires small low-energy cutoff at all times

June 19, 2003AAS/SPD Meeting6 2 Thermals + Power Law - Much better fit early on, but ambiguous at later times; still somewhat incomplete

June 19, 2003AAS/SPD Meeting7 Analysis - methods and problems Low-T component dominant <15 keV –Iron feature is good measure of thermal component Power law dominant >30-35 keV –Spectral index fairly easy to fit, but… Low-E cutoff very hard to determine –Power law & High-T component interfere

June 19, 2003AAS/SPD Meeting8 Low-T component dominates thermal energy High-T should vary smoothly - constraint on fit Spectral parameters, energies

June 19, 2003AAS/SPD Meeting9 Conclusions Forward modeling gives ambiguous results –Still provides a reasonable first estimate of energies High-T component complicates analysis Calculate SXI-derived T, EM time profiles Continue analysis for variety of flares –More cases may help determine low-E cutoff Future Work