Time evolution and morphological characteristics of white light flare on 18 January 1989
Yunnan Observatory, P.O. Box 110, Kunming 650011, China
2 CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, China
Accepted: 4 September 1997
Some properties of the white light flare (WLF) that occurred on 18 January 1989 are presented. The flare consisted of 7 patched-shape kernels, with sizes cm2. The lifetimes of the kernels were from several minutes to more than 40 minutes. The initial bright points of the WLF kernels originated between the umbra and penumbra, in penumbra fibrils, between penumbra fibrils and the photosphere, or on the photosphere and light bridge. These kernels appeared 2 to 3 minutes after Hα flares, and reached their maxima respectively before the first maximum and 1 to 2 minutes before the second maximum of the Hα flare, and disappeared slowly before the disappearance of the Hα flare. The direction and size of material motion in the kernels are different. The precursors of the WLF are similar to those of ordinary flares. The magnetic pattern of the photosphere in the active region is in δ- structure, and the kernels lie at or near the changing magnetic neutral lines. The small longitudinal field gradient may be constrained by the small transverse field on the photosphere. The flare exhibited both temporal and spatial properties in the center reversal and line-width of Hα profiles, and has characteristics of both class I and II. Thus it may be a mixed-class white light flare.
Key words: sun: flares
© European Southern Observatory (ESO), 1998