Spatial development of X-ray emission during the impulsive phase of a solar flare

Abstract

The flare of 11 November, 1980, 17∶25 UT occurred in a magnetically complex region. It was preceded by some ten minutes by a gradual flare originating over the magnetic inversion line, close to a small sunspot. This seems to have triggered the main flare (at 70 000 km distance) which originated between a large sunspot and the inversion line. The main flare started at 17∶23∶20 UT with a slight enhancement of hard X-rays (E > 30 keV) accompanied by the formation of a dark loop between two Hα bright ribbons. In 3–8 keV X-rays a southward expansion started at the same time, with ν ∼- 500 km s −1. At the same time a surge-like expansion started. It was observable slightly later in Hα, with southward velocities of ≳ 200 km s−1. The dark Hα loop dissolved at ∼ 17∶24 UT at which time several impulsive phenomena started such as a complex of hard X-ray bursts localized in a small area. At the end of the impulsive phase at 17∶25∶40 UT, a coronal explosion occurred directed southward with an initial expansion velocity of ∼ 1800 km s−1, decreasing in 40 s to ∼500 km s−1.