EVOLUTION OF A DELTA-GROUP IN THE PHOTOSPHERE AND CORONA

We present a study of the evolution of NOAA AR 7205 in the photosphere and corona, including an analysis of sunspot motions, and show the ev olutionary aspects of flare activity using full-disc white-light obser vations from Debrecen, Vector magnetograms from Mees Observatory, Hawa ii, and Yohkoh soft X-ray observations. NOAA AR 7205 was born on the d isc on 18 June, 1992. During the first 3 days it consisted of intermit tent minor spots. A vigorous evolution started on 21 June when, throug h the emergence and merging (v approximate to 100-150 m s(-1)) of seve ral bipoles, a major bipolar sunspot group was formed. Transverse magn etic fields and currents indicated the presence of shear (clockwise tw ist) already on 21 June (with alpha approximate to 0.015 Mm(-1)). On 2 3 June, new flux emerged in the trailing part of the region with the n ew negative polarity spot situated Very close to the big positive pola rity trailing spot of the main bipole. The secondary bipole seemed to emerge with high non-potentality (currents). From that time the AR bec ame the site of recurrent Rare activity. We find that all 14 flares ob served with the Yohkoh satellite occurred between the highly sheared n ew bipole and the double-headed principal bipole. Currents observed in the active region became stronger and more extended with time. We pro pose that the currents have been (i) induced by sunspot motions and (i i) increased by non-potential flux emergence leading to the occurrence of energetic flares (X1.8 and X3.9). This observation underlines the importance of Bare analysis in the context of active region evolution.