Solar active region spectra at submillimetric wavelengths

Details Solar active region spectra at submillimetric wavelengths Solar active region spectra at submillimetric wavelengths

Aug 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003basbr..23q.183s&link_type=abstract

Boletim da Sociedade Astronômica Brasileira (ISSN 0101-3440), vol.23, no.1, p. 183-183

Astronomy and Astrophysics

Astronomy

Scientific paper

Solar maps at 212 and 405 GHz obtained by the Solar Submillimetric Telescope (SST) show regions of enhanced temperature, which coincide with the location of active regions. A statistical study of the radio emission from these active regions was performed for the first time at such high frequencies. During 23 days when the atmospheric opacity was low, the brightest regions on the maps were chosen for this study. The antenna temperature excess observed in these regions varies from 2-10% (i.e., 150 to 550 K) above quiet Sun levels at both wavelengths, and the flux density spectra of these sources are essentially flat. Assuming the source of radio emission to have a Gaussian shape, sizes of 2-7 arcmin were estimated. In order to derive physical parameters for the submm active region sources, maps at 17 and 34 GHz from the Nobeyama Radio Heliograph were also used. These high resolution interferometric maps were convolved with a Gaussian beam of 4' HPBW, so as to be compared with the submm data. The resulting spectra at all 4 frequencies were successfully fit by thermal bremsstrahlung emission. The physical parameters obtained from this fit are: electron temperatures, ambient densities, and source diameters. The temperature values resulting from the fits are consistent with chromospheric values, thus confirming that the submm emission originates from sources located in the chromosphere.

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