We introduce a new method for imaging spectroscopy analysis of hard X-ray emission during solar flares. The new method allows the construction of images of both count and electron flux spectra that are smoothed with respect to energy, and so more suitable for further analysis. The procedure involves regularized inversion of the count visibility spectra (i.e., the two-dimensional spatial Fourier transforms of the spectral image) to obtain smoothed forms of the corresponding electron visibility spectra. We apply the method to a solar flare observed on February 20, 2002 by the RHESSI instrument. The event is characterized by two bright footpoints with a "strand" of more diffuse emission between them. We find that the electron flux spectra at the footpoints are systematically harder than those in the region between the footpoints, and that the observed degree of hardening is consistent with that produced by Coulomb collisions between an acceleration site high in the corona and the dense chromospheric footpoint regions.
Determination of electron flux spectrum images in solar flares using regularized analysis of hard X-ray source visibilities / A. G., Emslie; M., Piana; A. M., Massone; G. J., Hurford; Prato, Marco; E. P., Kontar; R. A., Schwartz. - In: BULLETIN OF THE AMERICAN ASTRONOMICAL SOCIETY. - ISSN 0002-7537. - STAMPA. - 39:(2007), pp. 037.04-037.04. (Intervento presentato al convegno American Astronomical Society 210th Meeting tenutosi a Honolulu, HI (USA) nel 27-31 maggio 2007).
Determination of electron flux spectrum images in solar flares using regularized analysis of hard X-ray source visibilities
PRATO, Marco;
2007
Abstract
We introduce a new method for imaging spectroscopy analysis of hard X-ray emission during solar flares. The new method allows the construction of images of both count and electron flux spectra that are smoothed with respect to energy, and so more suitable for further analysis. The procedure involves regularized inversion of the count visibility spectra (i.e., the two-dimensional spatial Fourier transforms of the spectral image) to obtain smoothed forms of the corresponding electron visibility spectra. We apply the method to a solar flare observed on February 20, 2002 by the RHESSI instrument. The event is characterized by two bright footpoints with a "strand" of more diffuse emission between them. We find that the electron flux spectra at the footpoints are systematically harder than those in the region between the footpoints, and that the observed degree of hardening is consistent with that produced by Coulomb collisions between an acceleration site high in the corona and the dense chromospheric footpoint regions.
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