Simultaneous SMM Flat Crystal Spectrometer and Very Large Array Observations of Solar Active Regions,
TUFTS UNIV MEDFORD MA DEPT OF PHYSICS AND ASTRONOMY
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We compare high-resolution images of the quiescent emission from two solar active regions at 20 cm VLA and soft X-ray SMM-FCS wavelengths. There are regions where the X-ray coronal loops have been completely imaged at 20 cm wavelength. In other regions, the X-ray radiation was detected without detectable 20 cm radiation, and vice versa. The X-ray data were used to infer average electron temperatures Te of about 3,000000 K and average electron densities of about 2.5 x ten to the ninth power cc for the X-ray emitting plasma in the two active regions. The thermal bremsstrahlung of the X-ray emitting plasma is probably optically thin at 20 cm wavelength. Although the 20-cm brightness temperatures TB were always less than Te, suggesting optically thin layers, the thermal gyroresonance radiation from the X-ray emitting plasma ought to be optically thick at 20 cm wavelength. The low TB can be explained if a higher, cooler plasma covers the hotter X-ray emitting plasma. Thermal gyroresonance radiation must account for the intense 20-cm radiation near and above sunspots where no X-ray radiation is detected. The potential of 20-cm VLA and soft X-ray SMM-FCS comparisons is discussed.