HEAD 2003 Meeting
Session 12. Protostars, Stars and Instrumentation III
Poster, Sunday-Wednesday, March 23, 2003, Duration of Meeting

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[12.03] Measuring Hard X-Ray Polarization of Solar Flares with RHESSI

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

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 (30-100 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. Current estimates suggested that a 30-100 keV polarization sensitivity of less than a few percent could be achieved for X-class flares. We shall describe this detection process in detail and present results from detailed simulations of the polarimetric capability of RHESSI. Finally, we shall review the latest results from our efforts to measure polarization from the class X4.3 flare that took place on 23 July 2002. These data show a modulation of the flux that may be due, in part, to polarization.

The author(s) of this abstract have provided an email address for comments about the abstract: Mark.McConnell@unh.edu

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Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.