Multiple Wavelength Observations of Flaring Active Regions

Abstract.

The radio emission of quiescent active regions at 6 cm wavelenght marks the legs of magnetic dipoles, and the emission at 20 cm wavelength delineates the radio wavelength counterpart of the coronal loops previously detected at X-ray wavelengths. At both wavelengths the temperatures have coronal values of a few million degress. The polarization of the radio emission specifies the structure and strength of the coronal magnetic field (H 600 Gauss at the heigths h 4 x 10⁹ cm above sunspot umbrae). At 6 cm and 20 cm wavelength the solar bursts have angular sizes between 5" and 30" brightness temperatures between 2 x 10⁷ K and 2 x 10⁸ K, and degrees of circular polarization between 10% and 90%. The location of the burst energy release is specified with second-of-acr accuracy. At redio wavelength the burst occur within the central regions of magnetic loops, while the flaring Hα kernels are located at the loop footpoints. Coronal loops exhibit enhanced radio emission (preburst heating) a few minutes before the release of burst energy. The radio polarization data indicate magnetic changes before and during solar bursts.