Reconstruction of RHESSI Solar Flare Images with a Forward Fitting Method |
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| Authors: | Aschwanden Markus J Schmahl Ed Team the RHESSI |
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| Institution: | (1) Solar & Astrophysics Laboratory, Dept. L9-41, Lockheed Martin ATC, Bldg.252, 3251 Hanover St., Palo Alto, CA, 94304, U.S.A.;(2) Solar & Astrophysics Laboratory, NASA Goddard Space Flight Center, USA |
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| Abstract: | We describe a forward-fitting method that has been developed to reconstruct hard X-ray images of solar flares from the Ramaty
High-Energy Solar Spectroscopic Imager (RHESSI), a Fourier imager with rotation-modulated collimators that was launched on
5 February 2002. The forward-fitting method is based on geometric models that represent a spatial map by a superposition of
multiple source structures, which are quantified by circular gaussians (4 parameters per source), elliptical gaussians (6
parameters), or curved ellipticals (7 parameters), designed to characterize real solar flare hard X-ray maps with a minimum
number of geometric elements. We describe and demonstrate the use of the forward-fitting algorithm. We perform some 500 simulations
of rotation-modulated time profiles of the 9 RHESSI detectors, based on single and multiple source structures, and perform
their image reconstruction. We quantify the fidelity of the image reconstruction, as function of photon statistics, and the
accuracy of retrieved source positions, widths, and fluxes. We outline applications for which the forward-fitting code is
most suitable, such as measurements of the energy-dependent altitude of energy loss near the limb, or footpoint separation
during flares.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022469811115 |
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