AAS 204th Meeting, June 2004
Session 2 When the Sun Went Wild
SPD Topical Related Poster, Monday, May 31, 2004, 9:20am-6:30pm, Ballroom

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[2.07] RHESSI Studies of Solar Flare Hard X-Ray Polarization

M. L. McConnell, J M. Ryan (UNH), D. M. Smith (UCSC), A. G. Emslie (UAH), M. Fivian, G. J. Hurford, R. P. Lin (UCB)

Although designed primarily as a hard X-ray imager and spectrometer, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) is also capable of measuring the polarization of hard X-rays (20-100 keV) from solar flares. This capability arises from the inclusion of a small unobstructed Be scattering element that is strategically located within the cryostat that houses the array of nine Germanium detectors. The Germanium detectors are segmented, with both a front and rear active volume. Low energy photons (below about 100 keV) can reach a rear segment of a Ge detector only indirectly, by scattering. Low energy photons from the Sun have a direct path to the Be and have a high probability of Compton scattering into a rear segment of a Ge detector. The azimuthal distribution of these scattered photons carries with it a signature of the linear polarization of the incident flux. Since its launch, RHESSI has observed a number of X-class solar flares. We will present the latest results on our evidence for hard X-ray polarization from the X4.3 flare that took place on 23 July 2002. In addition, we will present the first results from an analysis of events from October and November of 2003.

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