CORONAL TEMPERATURE, DENSITY, AND MAGNETIC-FIELD MAPS OF A SOLAR ACTIVE-REGION USING THE OWENS VALLEY SOLAR-ARRAY

We present the first results of solar active region observations with the recently completed five-element Owens Valley Solar Array. On 1991 October 24, maps of Active Region AR 6891 were obtained at 22 frequenc ies from 1.2-7.0 GHz to provide brightness temperature spectra at each point. This is the first time that both high spatial and frequency-re solution brightness temperature spectra have been available over such a broad radio-frequency range. We find that over most of the region th e spectra fall into one of two well-defined categories: thermal free-f ree or thermal gyroresonance. In these cases, we use the spectra to de duce the spatial variation of physical parameters-electron temperature , column emission measure (integral n(e)(2) dl), and coronal magnetic field strength-in and around the active region. Over a limited area of the region, the spectra resemble neither of the simple types, and alt ernative interpretations are required. The possibilities include the p resence of fine structure that is unresolved at low frequencies; the p resence of a small number of nonthermal electrons; or the presence of overlying, cooler (10(6) K) material which at low frequencies absorbs the hot (3 x 10(6) K) thermal emission generated below.