Free access article

A&A 381, 694-702 (2002)
DOI: 10.1051/0004-6361:20011556

First detection of the impulsive and extended phases of a solar radio burst above 200 GHz

G. Trottet¹, J.-P. Raulin², P. Kaufmann², M. Siarkowski³, K.-L. Klein¹ and D. E. Gary<sup>4

1</sup>  DASOP, CNRS-UMR 8645, Observatoire de Paris, Section de Meudon, 92195 Meudon, France
²  CRAAE/CRAAM, Instituto Presbiteriano Mackenzie, Rua da Consolação 896, 01302-907 São Paulo, Brazil
³  Space Research Center, Polish Academy of Sciences, ul. Kopernika 11, 51-622 Wroclaw, Poland
⁴  NJIT, Center for Solar Research, 323 M L King Blvd., Newark, NJ 07102, USA

(Received 20 September 2001 / Accepted 24 October 2001)

Abstract
We present a detailed analysis of radio observations obtained at 212 and 405 GHz during the 2000 March 22 H 2N flare that occured in AR8910 at ~1834 UT. These data are compared with microwave, soft X-ray and hard X-ray measurements of this flare. While the flare emission is not clearly detected at 405 GHz, the time profile of the 212 GHz emission exhibits an impulsive burst, associated in time with the 1-18 GHz impulsive microwave burst and a long-lasting thermal burst which finishes at about the same time as the soft X-ray emission but reaches its maximum later. The 212 GHz impulsive emission and the lack of detection at 405 GHz are consistent with synchrotron radiation from a population of ultrarelativistic electrons in an average magnetic field of 400-600 G. This radiating population of electrons has a hard energy spectrum (power law index 2.7). The expected >1 MeV gamma-ray continuum emission from the radio emitting electrons is comparable to that detected for mid-size electron-dominated events and the hard X-ray flux they would produce at 100 keV is consistently lower than the upper limit inferred from the observations. It is shown that the 212 GHz thermal source has to be different from that radiating the soft X-ray and microwave thermal emission. The present observations of a solar burst provide the first evidence of the extension of the gyrosynchrotron spectrum of an impulsive radio burst in the synchrotron domain above 200 GHz.

Key words: Sun: activity -- flares -- particle emission -- radio radiation

Offprint request: G. Trottet, gerard.trottet@obspn.fr

© ESO 2002

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

• If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
• You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
• You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.