The Large Flare on July 14 in 1980 and the Velocity Field

A series of flares and a small proton event erupted in the sunspot active region (which was assigned the Yunnan Observatory Serial Number (80) 369, or the Boulder Serial Number 2562, or the Hale Region Serial Number 16978) during its passage across the solar disc (from July 11 to July 23 in 1980).A 3B optical flare in the region was observed at the H α chromospheric telescope (with the aperture of 12 cm and the bandwidth of 0.75Å) on the 14th in July (see Att. Fig. 3). The fine-structure photographs of the sunspots (taken at a telescope with the aperture of 5 inches and the image diameter of 30 cm, see Att. Fig. 4), the data of the strong magnetic field of the sunspots and S HG in the descending phase of the flare (at a telescope with the aperture of 40 cm, the image diameter is 15.2 cm, the scanning interval is 4".2 and the area on the solar disc is 252"×189") have been obtained.It is shown from Att. Fig. 3 and Fig.5 that based on the continuous variations of the photospheric filaments and the brightening of the chromospheric plages before the flare, the flare erupted inside the active filament in the shape of a dipper and on either side of the handle of the dipper.The main, part of the flare was consistently restricted by the filament, did not cover the sunspot C and finally, disintegrated in the southeastern direction of C.according to the measurement of the strong magnetic field of photosphcric sunspots the flare was far away from the magnetic neutral line and the neutral line ran parallel to the reversal line of the velocity on the whole (see Fig.2.)The distribution of the radial velocity is shown in Fig.2 from the measurement in Att. Fig. 4. The results are as follows: 1. The flare was located on either side of the reversal (or zero) line of the radial velocity. The result is in accordance with that obtained by K. L. Harvey and J. W. Harvey.Rayrole has shown that the necessary condition of the appearence of a flare is the existence of the shearing motion near the flare. Obviously, this condition is satisfied near the reversal line of the radial velocity.2. During the flare eruption, the neighbouring filament moved violently, and the velocities of all parts of it were different, ranging from-28.9 kms^-1 to +73.1 kms^-1. The more distant part of the filament is comparatively quiet (see the top left of Fig. 2). If the eruption of flare is related to the emergence of.the new magnetic flow, the above-mentioned result is significant.3. No apparent rolling of the filament was observed. The active filament was divided into three parts by the reversal line of the radial velocity, the middle one descended and the others ascended. The masimum descent vel ocity and ascent velocity of the chromospheric matter in the active region were almots concentrated on the filament.4. The below right region of the velocity field had the ascent velocity which was smaller than 20 kms^-1, but no active object corresponded to the region.5. The measurement of the spectra shows that the weak sbsorption lines near the Ha line did not shift, which seemed to indicate that the turbulence of the flare was limited to the chromosphere and had no effect on the photo-spheric matter.