4dv. Space Res. Vol. 6. No. 6. pp. 21—N. I9~o M2~—1 l’~ .~ SU It) Printed n Great Brttain. All rights reserved C~p~ri~ht ~ COSPAR SUNSPOT PROPER MOTIONS IN CONNECTION WITH THE WHITE- LIGHT FLARE OF 25 APRIL 1984 L. Gesztelyi and B. Kálmãn Heliophysical Observatory of the Hungarian Academy of Sciences, P.O. Box 30, 1-1-4010 Debrecen, Hungary ABSTRACT During the descending phase of the present cycle of solar activity one of the largest events was the 3B/X13.O white—light flare in NOAA Active Region No. 4474 near the eastern limb on 24/25 April 1984. We present a study of the evolution of the very complex and extended active region 4474, the proper motion of the sunspots and the changes in the magnetic field in con- nection with the large flare, with special emphasis on the magnetic shear and other possible types of motion leading to flare build—tap, and following the flare. INTRODUCTION The flare of 24/25 April 1984 was the second largest in X—rays ever observed 0(13.0, the lar- gest, X15 was the one of 11 July 1978). This event was also observed in white light /1,2,3/. The active region was very complex, so it deserved a detailed study of proper motions of the sunspot umbrae, in Connection with the flare. In the present paper we restrict ourselves to the propermotionsbetween 22—28April, around the white—light flare. A more extended account, considering the whole disk passage of the region and also the neighbouring ones is in prepa- ration. A study of coronal turbulence above this region in quiet state was performed by Saba and Strong /4/. - THE OBSERVING MATERIAL In the following analysis we used white—light full disk photoheliograms with 10 cm image dia- meter, made in the Debrecen Observatory and in its Gyula Observing Station, observers were 0. Gerlei in Debrecen, Mrs. Zs. Lengyel and L. Gy6ri in Gyuls. In the period of 22—28 April there were 53 observations in Debrecen and 43 in Gyula, in Gyula there was no observation on 25 April. We used also white—light photographic observations of the Tokyo Astronomical Obser- vatory, including the flare, kindly provided by E. Hiei, white—light and H—alpha observations of the Hida observatory (courtesy H. Kurokawa), these were around 0h UT, and were of great help in identification of the sunspots from one day to the next. Finally the magnetic field was studied on a vector—magnetogram from the Marshall Space Flight Center, kindly sent by M. Hagyard. The reduction of the photoheliograms followed the usual procedure in the Debrecen Observato- ry /5/, the computer program includes corrections for differential refraction and for instru- mental errors, particularly for distortion of the enlarging system and for plate tilt. Using the computed heliographic coordinates, rectified drawings of the active region were made by a Hewlett—Packard 9810A calculator of the Debrecen Observatory, equipped by a digitizer and a plotter. RESULTS AND DISCUSSION Figure 1 shows the evolution of the sunspot groups in NOAA Active Region 4474 in the period 22—28 April, the rectified drawings in Carrington coordinates, showing also the designations of the umbrae. Numbers denote umbrae of preceding (negative) polarity, letters — of following (positive) magnetic polarity. From the magnetic polarities can be seen, that the active region contained in the beginning four, at the end six bipolar sunspot groups. In the order of appea— rence, the first consists of the moderately quiet p spot of 50/51, the f part of this group from 22 to 25 April forms a delta—configuration (umbrae 55 and N) . It is interesting to note that this small delta—configuration separates after the large flare, in the night from 25 to 26 April. The next group is the large complex, consisting of the spots 1—10 and A—D. The white—light flare occurred in the northern part of this group /1,2,3/. The third also large and complex 21