Estimation of coronal magnetic field from razin effect in solar decametric continuum burst

Abstract

A solar flare of importance 1B which occurred at 06:36 UT on April 27, 1979 on the solar disk (N 20, E 16) produced intense radio bursts. The most interesting feature of this event is the observation of a strong continuum radiation (type IV) starting at 06:53 UT and lasting for about 10 min in the decametric range. This continuum radiation displayed sharp low frequency cut-off, which varied from about 40 to 30 MHz in a quasiperiodic manner and could be attributed to Razin effect. The perturbation of this cut-off frequency is interpreted as that induced by the passing MHD shock wave through the region of the trapped energetic electrons. Assuming model electron density values and using the observed cut-off frequency, the magnitude of coronal magnetic field around 2R from Sun center works out to be about 6 G.