A THEORETICAL MODEL FOR TYPE II SOLAR RADIO BURSTS.

摘要

A new approach to Type II radio bursts is considered. Excitation of such radio bursts is taken to occur as the result of electron-electron two-stream processes in double-layer regions which are formed in the front and at the rear boundary regions of supersonic proton streams. Such streams which move through the solar corona with speeds V(,p) < 1000 km/sec are formed during the annihilation process of magnetic fields in the flash phase of a solar flare. It is shown that the proton stream and double-layer structure can form a self-consistent system which is specified by double-layer conditions as described in Carlqvist's theory. A BGK approach is used to estimate the double-layer length scale L(,DL) (DBLTURN) 1 meter which corresponds to a double-layer potential drop (phi)(,0) (DBLTURN) 10('5) volts. Band splitting in Type II radio bursts is accounted for by our model. The splitting is a consequence of the different values of the coronal plasma frequency at the front and at the rear boundary double-layer regions of the proton stream. On the basis of this model an estimate of the Type II radio brightness temperature T(,b) (DBLTURN) 10('11)(DEGREES)K is obtained which is in agreement with the observed order-of-magnitude.