Sunspot gyroresonance emission at 17 GHz: A statistical study

We investigate the sunspot gyroresonance emission at 17 GHz using the synoptic database of the Nobeyama Radioheliograph. Our statistical Study is based on full disk observations obtained during the maximum of Cycle 22 (1992-94). We Study the center-to-limb variation of the brightness and polarization Of the Sunspot radio emission and present some cases of polarization reversal. We find that the radio emission is most likely 3rd-harmonic gyroresonance emission arising from 2000 G fields in transition region, or low corona temperatures.