VLA STEREOSCOPY OF SOLAR ACTIVE REGIONS .2. ALTITUDE, RELATIVE MOTION, AND CENTER-TO-LIMB DARKENING OF 20 CENTIMETER EMISSION

A newly developed method of stereoscopic correlation is applied to solar radio maps at a wavelength of 20 cm. On the basis of stereoscopic correlations..between radio maps obtained on 6 different days we establish the presence of 66 radio source components associated with 22 active regions. We find the following statistical results for active region source structures at 20 cm: 1. The observed lifetime is consistent with an exponential distribution having an e-folding time scale of > 18 days. 2. The average altitude of 20 cm sources is 25 +/- 15 Mm; 90% of the sources are found in heights < 40 Mm. 3. The average diameter of discrete source structures is 48 +/- 15 Mm, implying a vertical/horizontal aspect ratio of q(A) almost-equal-to 0.5. 4. No significant source motion has been found with respect to the standard differential rotation rate of OMEGA = 13.45-degrees - 3-degrees sin 2 B. 5. We find a statistical limb darkening, which can be described by the relation T(B)(alpha)/T(B)(0) = 0.4 +/- 0.6 cos2 alpha for sources with T(B) > 0.5 MK. 6. The degree of source polarization is 15% +/- 10% and is independent of source location. 7. Bright sources (greater-than-or-equal-to 0.5 MK), or equivalently, long-lived sources (greater-than-or-similar-to 5 days) show a systematic variation of their altitude as function of the center-limb distance. We investigated a number of homogeneous and inhomogeneous active region models and found that inhomogeneous (both temperature and density) models are required to reproduce all observational constraints.