Compact,variable sources on the Sun at 2 centimeter wavelength |
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| Authors: | Robert F Willson Kenneth R Lang |
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| Institution: | (1) Department of Physics and Astronomy, Tufts University, 02155 Medford, MA, USA |
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| Abstract: | Very Large Array (VLA) observations of compact transient sources on the Sun at 2 cm wavelength are presented. These sources have angular sizes of   5 –25, brightness temperatures of T
B 1–3 × 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 (N
e 1010 cm-3) plasma in the transition region. For other sources, the relatively high circular polarization (
c 40–50 %) suggests a nonthermal emission mechanism, such as the gyrosynchrotron radiation of mildly relativistic electron with a power-law spectrum. |
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