JOINT RADIO AND SOFT-X-RAY IMAGING OF AN ANEMONE ACTIVE-REGION

The Very Large Array and the Soft X-ray Telescope (SXT) aboard the Yoh koh satellite jointly observed the rapid growth and decay of a so-call ed 'anemone' active region on 3-6 April, 1992 (AR 7124). The VLA obtai ned maps of the AR 7124 at 1.5, 4.7, and 8.4 GHz. In general, discrete coronal loop systems are rarely resolved at 1.5 GHz wavelengths becau se of limited brightness contrast due to optical depth effects and wav e scattering. Due to its unusual anemone-like morphology, however, sev eral discrete loops or loop systems are resolved by both the VLA at 1. 5 GHz and the SXT in AR 7124. Using extrapolations of the photospheric field and the radio observations at 4.7 and 8.4 GHz, we find that the microwave emission is the result of gyroresonance emission from a hot , rarefied plasma, at the second and/or third harmonic. The decimetric source is complex - 1.5 GHz emission from the leading part of AR 7124 is due to free-free emission, while that in the trailing part of the active region is dominated by gyroresonance emission. We also examine an interesting case of a discrete radio loop with no soft X-ray (SXR) emission adjacent to a hot SXR loop. This observation clearly shows th e multithermal nature of the solar corona.