Using observational data of sunspots, Ha chromospheric region, solar flux at 10.7 cm, solar magnetic field and soft X-ray emissions in 1-8 Å, the evolution of the Active Region 4711 which produced major flares early in the February, 1986 is described. The characteristics of the evolution of the region are discussed and the conclusions are as follows:(1) The sunspot group in the region is classified as DKCor EKCand Delta in the main phase of its development, and forms a compact, complicated and strong magnetic area during its main active stage.(2) Two large flares on 4th, February (3B/X3) and on 6th, February (3B/X1.7), respectively, occurred in the beginning stage of the descending phase of the sunspot group. The lifetime of the descending phase is about two times that of the ascending phase of the sunspot group.(3) The rotation of the sunspot group seems to be the energy mechanism for the heating and flares in the region. The rate of generation of magnetic energy estimated is 6×10
27.6 erg/ sec and 5×10
32.6 erg/day for the period from 3th to 4th, February, and 4×10
27.6 erg/sec and 3.4×10
32.6 erg/day for the period from 4th to 5th, February. The most part of the generated energy would be taken away by the Alfven weve, and a small part of it is enough for flares.(4) Frequent activities of Ha filaments in the region are the precursor of a large flare. The chromospheric fibers arranged in good order in the region should imply a strong transverse field.(5) The daily radio flux at 10.7 cm estimated for the active region has two peaks. One of them coincides with the peak of the area of the sunspot group. The other coincides with the CMPof the sunspot group. The daily minimum flux obtained from the soft X-ray plot by GOES-5 is assumed to represent the state of thermal coronalplasma. Two peaks of the flux are not to coincide with those of 10.7 cm flux and the sunspot area. The minimum flux of the soft X-ray (1-8 A) seems to be affected by large flares strongly.
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