CHARACTERISTICS OF CORONAL SHOCK-WAVES AND SOLAR TYPE-II RADIO-BURSTS

In the solar corona shock waves can be generated by coronal mass eject ions and solar flares. They manifest themselves in solar type II radio bursts. These special bursts appear as narrow emission stripes drifti ng slowly from high to low frequencies in dynamic radio spectra. A sam ple of 25 solar type II radio bursts observed in the range of 40-170 M Hz by the radio spectrograph of the Astrophysikalisches Institut Potsd am is investigated concerning their spectral features, i.e., drift rat e and instantaneous bandwidth. Plasma waves measurements interplanetar y shock waves provide the assumption that type II radio emission is or iginated in the vicinity of the transition region of shock waves. Thus , the instantaneous bandwidth of a solar type II radio burst would ref lect the density jump across the associated shock wave. In the framewo rk of magnetohydrodynamics the Rankine-Hugoniot relations of shock wav es are investigated under circumstances of the upper corona. Comparing these results with those obtained from the observational study solar type II radio bursts should be considered to be generated either by we ak supercritical, quasi-parallel, or by subcritical, quasi-perpendicul ar fast magnetosonic shock waves in the corona.