Radio evidence of directive shock-wave propagation in the solar corona

Abstract

Radioheliograph observations at 80 MHz are reported of a flare-associated event in which two type II bursts occur in four different sources. The projected centres of the sources lie along an arc subtending an angle of about 150° at the optical flare centre. If the arc represents the projection on the Sun's disk of a shock front passing through the 80 MHz plasma level, the source configuration suggests that the shock wave has originated from the optical flare region and propagated into the corona within a limited cone. On the opposite side of the flare centre, outside the shock cone, there was a stable bipolar source. Strong magnetic fields in this source may have acted as a ‘magnetic wall’ to the shock wave and inhibited its propagation in this direction.