The circularly polarized sun at 12.6 CM wavelength

Circular polarization maps of the Sun with 45arcsec angular resolution at 12 cm wavelength are presented. The maps show an excellent correlation with photospheric magnetograms. A similar correlation exists at 6 cm and 20 cm, and the brightness temperature of the circularly polarized emission is T_B ≡ 10⁶K. This suggests that the emission at all three wavelengths is due to the same hot plasma radiating in the presence of magnetic fields. 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 within the low solar corona. An alternative explanation is polarization by bremsstrahlung propagating in magnetic fields of strength H_l ≡ 100 Gauss and 50 Gauss, respectively. This probably applies to the regions that are not near sunspots.