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Astron. Astrophys. 317, 223-231 (1997)


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The impulsive phase of the arcade flare of 28 June 1992, 14:24 UT

M. Tomczak

Astronomical Institute, Wrocaw University, Kopernika 11, PL-51-622 Wrocaw, Poland (e-mail: tomczak@astro.uni.wroc.pl)

Received 5 January 1996 / Accepted 22 April 1996

Abstract

Yohkoh Soft X-Ray Telescope and Hard X-Ray Telescope observations of an M 1.6 limb flare of 28 June 1992, 14:24 UT have been analyzed. The flare occurred in a magnetic arcade. Basic observational characteristics of soft and hard X-ray emission for this flare have been compared. Excellent examples of impulsive soft X-ray brightenings have been found. Velocities of the chromospheric evaporation have been estimated directly from the SXT images. Derived values 460-750 km s-1 are consistent with previous spectral observations, but greater than results of standard theoretical models. Two separated places of simultanous energy release at the top of the arcade have been found. These places showed a different behaviour but clear connection. The location of the low-lying hard X-ray emission sources above the footpoints of the arcade has been explained as a result of a magnetic field convergence. The importance of the impulsive soft X-ray brightenings in investigation of the precipitation of non-thermal electrons has been emphasized.

Key words: Sun: corona — Sun: flares — Sun: X — rays, gamma rays


© European Southern Observatory (ESO) 1997

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