Compact, variable sources on the Sun at 2 centimeter wavelength

✍ Scribed by Robert F. Willson; Kenneth R. Lang

• Publisher: Springer
• Year: 1988
• Tongue: English
• Weight: 882 KB
• Volume: 114
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00193070

✦ Synopsis

Very Large Array (VLA) observations of compact transient sources on the Sun at 2 cm wavelength are presented. These sources have angular sizes of 0~5"-25", brightness temperatures of T~ ~ 1-3 x 105 K, and lifetimes ranging between a few minutes to several hours. The emission originates in regions of diffuse plage and quiet Sun, where the photospheric magnetic fields are relatively weak (H < 100 G). In some cases the 2 cm radiation may be explained as the thermal bremsstrahlung of a dense (Are < 101~ cm-3) plasma in the transition region. For other sources, the relatively high circular polarization (Pc ~ 40-50 %) suggests a nonthermal emission mechanism, such as the gyrosynchrotron radiation of mildly relativistic electron with a power-law spectrum.