NONTHERMAL RADIO-EMISSION FROM PLANETARY-NEBULAE

In a recent analysis of the radio emission from the planetary nebula A 30, Dgani, Evans, & White claim that the emission, located in the inne r region, is probably dominated by nonthermal emission. We propose a m odel to explain this. We assume that the fast wind, blown by the centr al star of A30, carries a very weak magnetic field. The interaction of this wind with a cluster of dense condensations traps the magnetic fi eld lines for a long time and stretches them, leading to a strong magn etic field. If relativistic particles are formed as the fast wind is s hocked, then the enhanced magnetic field will result in nonthermal rad io emission. The typical nonthermal radio flux at 1 GHz can be up to s everal millijanskys. In order to detect the nonthermal emission, the e mitting region should be spatially resolved from the main optical nebu la. We list other planetary nebulae that may possess nonthermal radio emission.