VLA observations of compact, variable sources on the sun

Abstract

Observations of solar active region AR 4508, obtained at 2.1 and 20.7 cm using the C configuration of the VLA on June 4, 1984, are reported. Compact (5-arcsec) sources with brightness temperature 50,000-300,000 K and circular polarization 80-90 percent are detected at 2.1 cm in regions with magnetic fields 80 G or less and found to vary on times scales of 10-20 s and 30-60 min. The emission of the sources is attributed to power-law-spectrum gyrosynchrotron radiation from mildly relativistic electrons, and its variability is related to variations in either the magnetic field or the nonthermal-electron density.