AAS 200th meeting, Albuquerque, NM, June 2002
Session 76. First Results from RHESSI
SPD Oral, Thursday, June 6, 2002, 10:00-11:30am, Ballroom C

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[76.08] The Electron Number Problem Revisited with RHESSI Flare Observations

M.J. Aschwanden, D. Alexander, T. Metcalf, N. Nitta (LMSAL)

The Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) observed a number of solar flares since its launch on February 5, 2002. We analyze first images and spectra from this new mission, using a variety of image reconstruction methods, such as Clean, Pixon, Maximum Entropy (MEM), and Forward-Fitting. We obtain context images of the flare regions in EUV from SoHO/EIT and TRACE, and soft X-ray light curves from GOES. From RHESSI we reconstruct hard X-ray images with full uv-coverage in time intervals of the spin period (~4 s). RHESSI provides a substantially higher spatial resolution (~ 2") and spectral resolution than previous data from Yohkoh/HXT.

A longstanding problem in solar flare physics is the so-called electron number problem, which challenges a reconciliation between (1) the rate of injected electrons inferred from the observed hard X-ray photon spectrum in the framework of the thick-target model and the (2) the replenishment rate of electrons in the coronal acceleration volume. Thanks to the high spectral resolution of RHESSI we can for the first time properly separate the thermal and the non-thermal electron spectral components, and this way determine the injection rate of nonthermal electrons more accurately. In addition, imaging in many energy bands allows us to trace propagation and energy loss between the coronal acceleration site and the chromospheric thick-target site with higher accuracy, taking into account the partial energy loss of trapped and precipitating electrons. The goal of this investigation is to quantify the geometry, density, and inflows in the coronal acceleration region, which provides crucial constraints for the underlying magnetic reconnection process.

If you would like more information about this abstract, please follow the link to http://www.lmsal.com/~aschwand/hessi/. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: aschwanden@lmsal.com

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.