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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[18.12] Nobeyama Radio Heliograph and RHESSI Observations of the X1.5 Flare of April 21, 2002

M.R. Kundu, V.I. Garaimov, S.M. White (Department of Astronomy, University of Maryland, College Park, MD), S. Krucker (Space Sciences Laboratory, University of California-Berkeley, Berkeley, CA)

We present radio observations of the X1.5 flare of April 21, 2002, and complementary data from other wavelengths. This flare was fairly well observed by the spacecraft RHESSI and fully observed by the Nobeyama Radio Heliograph at 17 and 34 GHz. This long-duration event lasted more than 2 hours and features a beautful arcade of rising loops on the limb visible at X--ray, EUV and radio wavelengths. The main flare was preceded by a small event 90 minutes earlier showing a long EUV loop connecting well-separated radio and hard X-ray sources. The main flare itself starts with a compact radio and hard X-ray source at the eastern end of the region that is followed by emission close to the solar surface (well inside the solar limb) over a large region to the northwest. As the flare proceeds a large set of loops is seen to rise well above the solar limb. Distinct regions of radio emission with very different time behaviour can be identified in the radio images, and in particular a peculiar nonthermal 17 GHz source low in the corona at the base of the arcade is seen to turn on 30 minutes after the start of the impulsive phase. At about the same time an extremely intense burst of coherent radio emission is seen from 500 to 2000 MHz: we speculate that this lower-frequency burst is located at the top of the arcade of loops.


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Bulletin of the American Astronomical Society, 35 #3
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