S-Component Sources at 21 cm Wavelength in the Rising Phase of Cycle 23 |
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| Authors: | Tapping KF Cameron HT Willis AG |
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| Institution: | (1) Dominion Radio Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council, P.O. Box 248, Penticton, British Columbia, V2A 6J9, Canada;(2) Department of Astronomy and Astrophysics, University of Toronto, 60 St George St., Toronto, Ontario, M5S 3H8, Canada |
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| Abstract: | The Synthesis Radio Telescope at the Dominion Radio Astrophysical Observatory is being used to make a long-term study of the relationship between sources of the slowly-varying component at 21-cm wavelength and the active regions with which they are associated. Although the arc-minute angular resolution of the radio telescope is insufficient to map individual active regions, the unique capability of this radio telescope to map the whole solar disc in a single operation makes it useful for identifying and measuring sources of the slowly-varying component, which at this wavelength are largely due to free–free thermal emission from plasma concentrations trapped in active region magnetic fields. The brightness temperatures of the emission are higher in large, complex active regions, suggesting the plasma slab producing the emission is thicker and/or denser in such regions. We find also that the relationship between the brightness temperature and the size and complexity of the host region is a function of the phase of the 10–13-year solar activity cycle. |
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