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[PEM07-23] Characteristics in solar white-light flares based on radio observations
In this paper, we analyzed the 10 events (white-light: 4 events, no white-light: 6 events) among the 42 events, which were observed with Nobeyama Radio Heliograph (NoRH) and Nobeyama Radio Polarimeters (NoRP). GHz microwave are emitted by gyrosynchrotron from very-high energy (~MeV) accelerated electrons. The peak intensity in 17 and 35 GHz does not show any significant difference between the white-light and no white-light events. This indicates that such high-energy electrons does not contribute white-light enhancement. The spectrum of gyrosynchrotron emission usually has a peak frequency which corresponds to the turning point (turn-over frequency) between the optical thick part in the lower frequency range and the optically thin part in higher frequency range. The white-light flares show systematically high turn-over frequency than that of the no white-light events. The higher turn-over frequency might correspond to stronger magnetic field. This is consistent that white-light flares tend to be compact. As for the time evolution of the spectrum, the no white-light flares tend to show the spectral hardening. This indicates that the magnetic mirror effectively works in no white-light flares because of the weak magnetic field in the flare loop.