Delta-configurations: Flare activity and magnetic-field structure |
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| Authors: | S R Patty M J Hagyard |
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| Institution: | (1) The University of Alabama in Huntsville, 35899 Huntsville, AL, U.S.A.;(2) Space Science Laboratory, Marshall Space Flight Center, 35812 Huntsville, AL, U.S.A. |
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| Abstract: | Complex sunspots in four active regions of April and May 1980, all exhibiting regions of magnetic classification delta, were studied using data from the NASA Marshall Space Flight Center vector magnetograph. The vector magnetic field structure in the vicinity of each delta was determined, and the location of the deltas in each active region was correlated with the locations and types of flare activity for the regions. Two types of delta-configuration were found to exist, active and inactive, as defined by the relationships between magnetic field structure and activity. The active delta exhibited high flare activity, strong horizontal gradients of the longitudinal (line-of-sight) magnetic field component, a strong transverse (perpendicular to line-of-sight) component, and a highly non-potential orientation of the photospheric magnetic field, all indications of a highly sheared magnetic field. The inactive delta, on the other hand, exhibited little or no flare production, weaker horizontal gradients of the longitudinal component, weaker transverse components, and a nearly potential, non-sheared orientation of the magnetic field. We conclude that the presence of such sheared fields is the primary signature by which the active delta may be distinguished, and that it is this shear which produces the flare activity of the active delta.NASA Graduate Student Research Fellow. |
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