On 18 January 1989, solar activity in the active region AR 5312 enhanced obviously from 05:00 to 09:52UT, and ordinary flares appeared one after another (NOAA 1989). The active region was monitored with the multi-band optical instrument (see Table 4 (click here)) at Yunnan Observatory.
A series of H
filtergrams of the active region was obtained with
the vacuum solar telescope (Instrument 1, Wu et al. 1990) from
03:30 to 08:18UT on 18 January (see Table 3 (click here) and Fig. 1 (click here)).
The data of scanning photographs and synchronous H filtergrams of
the white light flare (S30 W65) were also obtained with the two-dimension
multi-band spectroheliograph SSHG (Instrument
2, Xuan & Lin 1993) in three wave bands (H
,
H
and H
) during five different time intervals from
07:00UT to 07:52UT (Xuan et al. 1991). In the meantime, fine
structure observations (see Figs. 2 (click here) and 3 (click here)) of sunspots in
the region were made with the solar photosphere telescope (Instrument 3,
see Table 4 (click here)) of Yunnan Observatory several days before and after
18 January. The longitudinal components of the magnetic field during the
same time interval were also obtained with the solar magnetic field
telescope (Ai & Hu 1986) at the Huairou Station of Beijing
Observatory (see Fig. 3 (click here)).
The lifetime of the WLF and sizes of the kernels before maximum (see
Table 5 (click here)) were obtained by comparing the spectral data with
H filtergrams. The spectral films were measured with a PDS
microdensitometer and processed on a VAX-8350 computer. The changes of the
spectral line profiles in the WLF kernels are shown in Fig. 4 (click here) (see
Sect. 3.3).