RADIO-EMISSION FROM SOLAR-FLARES

Radio emission from solar flares offers a number of unique diagnostic tools to address long-standing questions about energy release, plasma heating, particle acceleration, and particle transport in magnetized p lasmas. At millimeter and centimeter wavelengths, incoherent gyrosynch rotron emission from electrons with energies of tens of kilo electron volts to several mega electron volts plays a dominant role. These elec trons carry a significant fraction of the energy released during the i mpulsive phase of flares. At decimeter and meter wavelengths, coherent plasma radiation can play a dominant role. Particularly important are type III and type III-like radio bursts, which are due to upward- and downward-directed beams of nonthermal electrons, presumed to originat e in the energy release site. With the launch of Yohkoh and the Compto n Gammn-Ray Observatory, the relationship between radio emission and e nergetic photon emissions has been clarified, In this review, recent p rogress on our understanding of radio emission from impulsive flares a nd its relation to X-ray emission is discussed, as well as energy rele ase in flare-like phenomena (microflares, nanoflares) and their hearin g on coronal heating.