Force-free magnetic fields and flares of August 1972 |
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| Authors: | K Tanaka Y Nakagawa |
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| Institution: | (1) High Altitude Observatory, National Center for Atmospheric Research, 80302 Boulder, Colo., U.S.A. |
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| Abstract: | On the basis of observations (Zirin and Tanaka, 1973) inferring the presence of shear in magnetic fields, the amount of extractable energy stored in a class of force-free magnetic fields is evaluated for the flares of August 1972, using the formulations developed by Nakagawa and Raadu (1972). It is shown that the evaluated energy storage could be built up by the proper motions of sunspots in the active region McMath 11976 during July 31 and August 7. Then for the flare of August 7, a detailed analysis is made of the manner of energy release in the post maximum phases deduced from the configuration of flare loops. It is shown that the observed flare loops could be represented closely by the force-free magnetic fields and that the evaluated rate of energy release is consistent with observed rate given by the soft X-ray emission. The results of analysis suggest that the flare of August 1972 could be identified with the relaxation of an energetic force-free magnetic field towards lower energy states. The limitations and possible future extension of this type of analysis are discussed.Visiting scientist from the Tokyo Astronomical Observatory, Mitaka, Tokyo, Japan.The National Center for Atmospheric Research is sponsored by the National Science Foundation. |
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