Preliminary studies of solar limb brightening at 8mm

Abstract

The investigation of the solar limb brightening can give information about various atmospheric structures of the Sun. In this study, preliminary investigations are made at the millimeter wavelength region. Data were obtained from Metsähovi Radio Observatory, Aalto University. The solar radio maps at 8 mm were used for the analysis. Data were only collected from the days of the low solar activity. We found limb brightening between 0.5 and 3 percent at the intermediate regions of the Sun. Our results are consistent with earlier reported results. There is no unambiguous explanation for the limb brightening, but spicules might be one possible source at higher radio frequencies. Also, the possible artificial effects are discussed.