Volume 409, Number 3, October III 2003
|Page(s)||1107 - 1125|
|Published online||17 November 2003|
A catalogue of white-light flares observed by Yohkoh*
Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
2 Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
3 Observatoire de Paris, section Meudon, LESIA (CNRS), 92195 Meudon Principal Cedex, France
4 Konkoly Observatory, Budapest, 1526, Hungary
5 Space Science Laboratory, UC Berkeley, CA 92740, USA
6 Lockheed Martin Solar and Astrophysics Laboratory, O/L9-41, B/252, 3251 Hanover Street, Palo Alto, CA 94304, USA
Corresponding author: S. A. Matthews, firstname.lastname@example.org
Accepted: 30 July 2003
The aspect camera of the Soft X-ray Telescope (SXT) on Yohkoh provided the first systematic survey of white-light flares from an observatory in space. The observations were made in the Fraunhofer g-band at a pixel size of 2.46 arcsec and a typical sample interval on the order of ten seconds. A total of 28 flares with clear white-light signatures were detected, corresponding to GOES events down to the C7.8 level in one case. Above the X-class threshold, all 5 events observed by SXT were observed in white light, and the maximum average contrast observed was 30% relative to the pre-flare continuum brightness of the flare location. We have made comprehensive comparisons of Yohkoh soft X-ray and hard X-ray data for this list of flares. In addition we compare the properties of the WLF sample to a sample of 31 flares that showed no white-light emission. These comparisons show that while white-light continuum emission has a strong association with hard X-ray emission it is also strongly related to coronal overpressure, as determined from the soft X-ray spectrum, indicating a component with a thermal, rather than non-thermal origin.
Key words: Sun: flares / Sun: X-rays, gamma rays
© ESO, 2003
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