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Astron. Astrophys. 317, 232-243 (1997)

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Evidence for highly inhomogeneous mm-wave sources during
the impulsive flare of May 9, 1991

R. Herrmann 1, A. Magun 1, P. Kaufmann 2, E. Correia 3, J.E.R. Costa 3, M.E. Machado 4 and G.J. Fishman 5

1 Institute of Applied Physics, University of Bern, Bern, Switzerland
2 Dept. of Physics, University of Alabama in Huntsville Alabama, USA and CONAE, Buenos Aires, Argentina
3 CRAAE/NUCATE, UNICAMP, Campinas, SP, Brazil
4 CRAAE/INPE, S. Paulo, SP, Brazil
5 Space Science Laboratory, NASA/MSFC, Alabama, USA

Received 16 February 1994 / Accepted 4 May 1996


In this paper multiwavelength observations of an impulsive flare of May 9, 1991 are presented. This event was observed with the 48 GHz multibeam focal array used at the Itapetinga radio telescope, the microwave patrol telescopes at Bern and the BATSE high time resolution hard X-ray spectrometer on board CGRO. While spatially unresolved low sensitivity observations show two major impulsive peaks, the mm-wave observations with the ability of spatially high resolved tracking of the emission centroids suggest a primarily bipolar source configuration. For the first time two mm-wave sources with a spacing below the HPBW could be separated with the multibeam technique. The general features of the observations are explained as emission of partially trapped electrons. Furthermore we present evidence for highly inhomogeneous substructures within one of the two mm-wave sources for which the positional scatter of the emission center, within 2 s, is less than 2".

Key words: Sun: flares — Sun: radio radiation — Sun: X-rays

Send offprint requests to: A. Magun

© European Southern Observatory (ESO) 1997