34th Solar Physics Division Meeting, June 2003
Session 18 RHESSI Results II
Poster, Wednesday, June 18, 2003, 3:30-5:00pm, Mezzanine

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[18.11] Comparison of methods for determining hard X-ray source sizes

E. J. Schmahl (Astronomy Dept, University of Maryland), G. J. Hurford (Space Science Lab, UC Berkeley)

The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) is capable of imaging hard X-ray flares with resolution as good as ~2 arcseconds. Knowledge of the spatial scales of sources is important for understanding the energetics of flares, the quantification of electron beaming, and for determining the existence and extent of albedo emission. Several methods of imaging are used by the RHESSI team for mapping, but some methods are more suitable than others for determining the spatial scales of X-ray sources. We have previously given results from two different Fourier methods, both deriving spatial scales from the relative amplitudes of RHESSI's modulation profiles, one using 'unpixelized forward fitting', and the other using 'normalized back-projection'. The equivalence of the two methods is not obvious, and our initial studies with the two techniques used different grid sets and different energy bands, so the results were not directly comparable. We have now used the two methods with precisely the same inputs and have found good ageeement between the derived spatial parameters. We will show examples of results for a variety of flares with spatial scales ranging from ~3'' to >30''.

This work was supported by NASA grants NAG 5-10180 and NAS 5-98033-05/03


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

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