On the role of beam driven return current instabilities in white-light flares
S.A. Matthews 1,
J.C. Brown 2 and
L. van Driel-Gesztelyi 3, 4
Received 9 July 1998 / Accepted 18 September 1998
It has been shown previously that the low ionization levels in the deep chromosphere of solar flares can cause the return current driven by a thick target electron beam to be unstable to ion aoustic wave generation, contrary to conventional wisdom. We investigate, using Yohkoh data, the possibility that anomalous heating as a result of this instability is capable of producing sufficient heating, in the right places at the right times, to account for the enhanced continuum emission actually observed in white-light flares. The Soft X-ray Telescope (SXT) onboard Yohkoh incorporates an aspect camera which, prior to its failure in 1992, provided white-light images at 431 nm with a bandpass of 3 nm. A number of white-light flares were observed during its operational lifetime for which there was coincident hard X-ray data from the Hard X-ray Telescope (HXT), providing suitable candidates for study. Four such events are discussed, and the model found to be viable.
Key words: Sun: activity Sun: flares Sun: X-rays, gamma rays
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© European Southern Observatory (ESO) 1998
Online publication: November 3, 1998