Very Large Array (VLA) Observations of Solar Active Regions

Abstract

Very Large Array (VLA) synthesis maps of the total intensity and the circular polarization of three active regions at 6 cm wavelength are presented. The radiation from each active region is dominated by a few intense cores with angular sizes of ~ 0.5′, brightness temperatures of ~ 106 K, and degrees of circular polarization of 30 to 90%. Some of the core sources within a given active region exhibit opposite senses of circular polarization, suggesting the feet of magnetic dipoles, and the high brightness temperatures suggest that these magnetic structures belong to the low solar corona. We also present comparisons between our VLA maps of circular polarization and Zeeman effect magnetograms of the lower lying photosphere. There is an excellent correlation between the magnetic structures inferred by the two methods, indicating that synthesis maps of circular polarization at 6 cm can be used to delineate magnetic structures in the low solar corona.