Analysis of Limb Brightening on the Quiet Sun at 21 Cm Using a Three-element Interferometer

During the summer, three small radio telescopes (SRTs) were used for observing the Sun during the Sun’s Quiet Phase almost daily over a two month period. We used the three SRTs as a 3-element interferometer to observe the entire Sun. The baselines used were 7.77 meters, 20.12 meters, and 26.67 meters. Data from the Sun were taken and software was used to calculate the visibility amplitudes and closure phase. A modeling program was used to replicate the Sun and a comparison of closure phases between the SRT data and the modeling data was performed with a weighted least-squares fit. We found evidence for limb brightening around the equatorial region of the Sun and determined that the modeling software fit the data better with limb brightening (the outer 20 percent of the solar disk’s diameter) used in conjunction with a translatable sunspot of varying brightness. The equatorial limb brightening was found to contribute 30 ± 10 percent of the total solar radio flux.