AAS 200th meeting, Albuquerque, NM, June 2002
Session 68. Flares
Display, Thursday, June 6, 2002, 9:20am-4:00pm, SW Exhibit Hall

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[68.04] The Effects of Low- and High-Energy Cutoffs on Solar Flare Microwave and Hard X-ray Spectra

G. D. Holman (LASP, NASA/GSFC)

Microwave and hard x-ray spectra provide crucial information about energetic electrons and their environment in solar flares. These spectra are becoming better determined with the Owens Valley Solar Array (OVSA) and the recent launch of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The proposed Frequency Agile Solar Radiotelescope (FASR) promises even greater advances in radio observations of solar flares.

Both microwave and hard x-ray spectra are sensitive to cutoffs in the electron distribution function. The determination of the high-energy cutoff from these spectra establishes the highest electron energies produced by the acceleration mechanism, while determination of the low-energy cutoff is crucial to establishing the total energy in accelerated electrons.

I will show computations of the effects of both high- and low-energy cutoffs on microwave and hard x-ray spectra. The optically thick portion of a microwave spectrum is enhanced and smoothed by a low-energy cutoff, while a hard x-ray spectrum is flattened below the cutoff energy. A high-energy cutoff steepens the microwave spectrum and increases the wavelength at which the spectrum peaks, while the hard x-ray spectrum begins to steepen at photon energies roughly an order of magnitude below the electron cutoff energy. I will discuss how flare microwave and hard x-ray spectra can be analyzed together to determine these electron cutoff energies.

This work is supported in part by the NASA Sun-Earth Connection Program.

The author(s) of this abstract have provided an email address for comments about the abstract: holman@stars.gsfc.nasa.gov

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.