Coronal Magnetic Structure near the Source Region of a Type II Radio Burst

The magnetic structure in the source region of a type II burst and along the path of the type II disturbance has remained an enigma despite over 20 years of radio observations of the Sun (see e.g. reviews by Wild and Smerd (1972) and McLean (1974)). This paper describes the first radioheliograph observations of a type II burst near coronal magnetic structures depicted by soft X-ray pictures. It will be shown that three separate lanes in a type II burst are associated with three separate source regions each located almost radially above a soft X-ray loop. To explain these observations a model is derived in which a wide-fronted m.h.d. disturbance travels from the flare explosion along magnetic field lines and then intersects successively with three coronal streamer structures each located above a soft X-ray loop. An estimate of the magnetic flux density along the soft X-ray loops is obtained from the velocity of the m.h.d. disturbance.