1-4 GHZ TYPE II-LIKE RADIO-BURSTS AND PINCH PROCESSES NEAR THE TRANSITION REGION

Analyzing 205 radio bursts observed by the Ondrejov radiospectrograph in the 1-4 GHz frequency range during 1992 and 1993, we found 6 exampl es of type II-like radio bursts coinciding with impulsive phases of so lar flares. These bursts were interpreted as radio manifestations of M HD (shock) waves generated during impulsive phases of flares in the vi cinity of the transition region. Assuming a magnetic-field perturbatio n origin of these waves, we studied pinch processes in the current she et near the transition region. In the 2-D MHD numerical model of this current sheet we demonstrated that 2-D pinch processes induced by radi ative losses can trigger the impulsive phase of some flares and so gen erate the observed high-frequency type II-like radio bursts.