AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 22. Solar Flares
Oral, Monday, May 31, 1999, 10:00-11:30am, Continental Ballroom B

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[22.03] Inversion of Spatially Resolved Hard X-Ray Spectra from HESSI

A. G. Emslie (Department of Physics, UAH)

The ability to resolve spatially the hard X-ray emission in a flare permits much closer analysis of particle acceleration and transport mechanisms. If the spatial resolution limit is significantly smaller than the collisional stopping length, then the hard X-ray emission in a given pixel can be treated as thin-target, and straightforward inversion of the hard X-ray spectrum gives the electron flux spectrum at that point in the flare. A study of how the electron spectrum varies from point to point, and with time at each point, supplies a considerable amount of information on the physical processes operating within the flare.

In preparation for the wealth of spatially-resolved hard X-ray spectra that will be provided by the forthcoming High Energy Solar Spectroscopic Imager (HESSI) mission, we have started to develop algorithms for analysis of this data. We shall show how considerations of continuity of electron number lead to straightforward expressions for the energy loss rate dE/dz as functions of energy E and position z. These expressions can then be compared to the expressions for known physical processes (such as Coulomb collisions)or used to infer the characteristics of the actual process(es) operating. Comparison of empirically determined energy loss rates with theoretical expressions for candidate mechanisms can also be used to constrain physical parameters, such as density and the magnetic field strength scale height.

This work was supported by NASA's Office of Space Science.

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