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Astron. Astrophys. 354, 691-696 (2000)


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On the origin of solar white-light flares

W.Q. Gan 1, J.C. Hénoux 2 and C. Fang 3

1 Purple Mountain Observatory, Nanjing 210008, P.R. China; National Astronomical Observatories, Chinese Academy of Sciences
2 Observatoire de Paris, DASOP, LPSH (UMR 8645), 92195 Meudon Principal Cedex, France
3 Department of Astronomy, Nanjing University, Nanjing 210093, P.R. China

Received 16 August 1999 / Accepted 7 December 1999

Abstract

Using the H[FORMULA] line intensity as a constraint, we study the role of a chromospheric condensation and the role of non-thermal effects in producing the continuum enhancement of white-light flares. Within an acceptable range of H[FORMULA] line intensities and electron energy flux, it is shown that neither a chromospheric condensation nor non-thermal effects alone can directly explain the observed continuum enhancement. The hybrid role of both chromospheric condensation and non-thermal effects can only lead to a Balmer jump, but still not to a significant continuum intensity increase between 4000 and 7000 Å. A possible picture is discussed, that is, the Balmer jump is directly produced by the association of a chromospheric condensation and of non-thermal effects, while the continuum enhancement between 4000 and 7000 Å is indirectly produced by the condensation and the non-thermal effects via radiative heating to the deeper photospheric layers.

Key words: Sun: flares – Sun: chromosphere – Sun: photosphere – Sun: X-rays, gamma rays

Send offprint requests to: W.Q. Gan

© European Southern Observatory (ESO) 2000

Online publication: February 9, 2000

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