VLA STEREOSCOPY OF SOLAR ACTIVE REGIONS .1. METHOD AND TESTS

We develop a new technique for extracting three-dimensional informatio n from multiday solar VLA observations. While standard stereoscopic me thods provide a three-dimensional view of an object by combining simul taneous observations from two different aspect angles, we relax the co ndition of simultaneity and exploit solar rotation to vary the aspect angle. The solar radio images are decomposed into Gaussian source comp onents, which are then cross-correlated in maps from preceding and fol lowing days. This provides measurements of the three-dimensional posit ion of correlated source centroids. In this first paper, we describe t he stereoscopic method and perform tests with simulated and real radio maps (from the VLA at 20 cm), in order to study the accuracy of altit ude measurements, and the limitations introduced by (i) source confusi on, (ii) source motion, and (iii) the assumed differential rotation ra te. The tests demonstrate that (i) the information content of a VLA ma p relevant for stereoscopic correlation can be conveniently represente d in terms of a small number of Gaussian components; (ii) the fitting of the three-dimensional source position is stable within a numerical accuracy of less-than-or-similar-to 0.02 map pixels; (iii) the relativ e accuracy of the altitude determination is uniform over the solar dis k, and (iv) source confusion does not affect the accuracy of stereosco pic position measurements for sources with a signal-to-noise ratio of greater-than-or-similar-to 36.