The Circularly Polarized Sun at 12.6 cm Wavelength.
TUFTS UNIV MEDFORD MA DEPT OF PHYSICS
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Circular polarization maps of the Sun with 45 sec angular resolution at 12 cm wavelength are presented for six continuous days. The maps have degrees of circular polarization up to pc 20, and they show an excellent correlation with photostatic magnetograms. A similar correlation exists at 6 cm and 20 cm, and at all three wavelentghs the brightness temperatures, TB, of the circularly polarized emission is TB approx 1,000,000 K. This suggests that the emission at all three wavelengths is due to the same hot plasma radiating in the presence of magnetic fields that project radially upwards from the photosphere into the low solar corona. At 6 cm wavelength highly circularly polarized pc appprox 50, core sources with angular sizes 0 approx 10 sec to 30 sec occur near sunspots. These core sources are due to gyroesonant emission at the third harmonic of the gyrofrequency, implying longitudinal magnetic field strengths of Hl approx 580 spots, gauss at altitudes h approx 3 x 10 to the ninth power cm above the sunspots. In regions near sunspots, the circularly polarized emission at 6 cm, 12 cm and 20 cm could all be due to the gyroemission of hot electrons spiralling in magnetic fields of strength Hl approx 280 gauss and Hl approc 170 guass are inferred from the 12 cm and 20 cm data, respectively. An alternative explanations is polarization by bremsstrahlung propagating in magnetic fields of strength Hl approx 100 guass and 50 gauss, respectively.