Studies of White-Light Flare on Jan. 18, 1989

In the present thesis, based onanalysing the synchronous filtergrams, two dimensional Hα spectra, quasi-synchronous photographs of sunspot and magnetograms of the active rgion NOAA /USAF: 5312 with a WLF appeared on January 18, 1989, we have studied the structures of sunspots, magnetic field of the active region and the time evolution of the WLF, and obtained the corresponding line-of-sight velocity field. Using the calculated line profiles as a diagnostic means, we disscussed the energy transport mechanisms and dynamical processes. The main conclusions are as follows: ①In active region NOAA 5312, the structure of the photospheric sunspot is complicated, the configuration of the magnetic field is of the δ-structure. Several main WL kernels lie at or near the magnetic neutral line, they originated at the juncture of umbra and penumbra and the juncture of penumbra and photosphere in penumbra or on the photosphere background. Before WLF appeared, chromospheric filaments were activated and disappeared rapidly, the fibrils in the place would be arranged in order. The WLF associated with plages tightly, but only the plages near some small activated, then disappeared filaments, and associated with subflares would probably induce WLF. ②The WLF consists of seven kernels with a dimension of around (1.5～4)×10¹⁷cm², and the life time of these kernels range from several minutes to more than 40 minutes. The contrast intensities of contimuum emissions are around 10% for Ha and up to 20% for Hγ, respectively. ③The velocity field of the WLF is also complicated, every WL kernel is near V_H=0 line with both small red and blue shifts ranging from-10 kms^-1 to +10 kms^-1. ④The Hα line profiles from these WL kernel sites are nearly symmetric except the central reversal. The profiles from some kernels are of absorption type and not intense, and the others are broad, intense and self-reversed with different red and blue peak intensities. ⑤It seems that high energy proton beam bombardment and dynamical energy transport by a chromospheric condensation are not important in this event. Some WL kernels probably originate from photosphere, and some WL kernels are probably caused by nonthermal electron beam bombardment. Finally, we have noticed that the present WLF might be an intermediate one which possesses both type Ⅰ and type Ⅱ WLF natures.