Electric Currents, and Magnetic Shear Variations During Some Flares of M- and X-Class
We study the magnetic field evolution during flares of M and X-class, using overlays of cotemporal Hα-filtergrams and magnetograms. Significant decrease in the area-averaged magnetic shear was found in some cases around the flare onset-time, increasing subsequently as the flare progressed. However, the changes were less pronounced for relatively smaller M-class flares. Strong Lorentz forces were found to exist at the photosphere, acting against the observed motions of sunspots. Extrapolated potential field indicated presence of a magnetic null at the upper chromosphere/lower coronal height, directly above a large Hα flare.
KeywordsLorentz Force Polarity Inversion Line Shear Parameter Filament Eruption Large Flare
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