The solar white-light flare of 1989 March 7 - Simultaneous multiwavelength observations at high time resolution

Abstract

Observational data for the March 7, 1989 white light flare (WLF) are presented. The flare kernel shows an impulsive rise in both H-alpha and continuum that is well correlated with impulsive hard X-rays. The H-alpha emission shows a red asymmetry interpreted as Doppler redshift associated with explosive heating of the chromosphere. The flare kernel is separated into a bright inner core and a fainter outer region, where the two components display distinctly different temporal behavior and amount of H-alpha and red asymmetry. A delay, relative to hard X-rays, of about 1 s is seen in the impulsive rise of the H-alpha wing emission, followed by an additional 1-2 s delay in the 5000 A continuum. The observed fluxes and timing of the hard X-ray and WLF optical emission are consistent with chromospheric heating by nonthermal electrons, with additional visible light continuum possibly being contributed by a backwarmed photosphere irradiated by intense chromospheric recombination continua.