Electric Currents, and Magnetic Shear Variations During Some Flares of M- and X-Class

  • Ashok Ambastha
  • J. M. Fontenla
  • Mona J. Hagyard


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.


Lorentz Force Polarity Inversion Line Shear Parameter Filament Eruption Large Flare 
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  1. Ambastha A., Hcigyard M.J., and West, E.A.: 1994, Solar Phys., 148, 277.ADSCrossRefGoogle Scholar
  2. Fontenla J.M., Ambastha A., Kaiman B., and Csepura Gy. 1995, Astrophys. J., 440, 894.ADSCrossRefGoogle Scholar
  3. Hagyard M.J., 1992, Mem. Soc. Astron. Ital. 61, 337.ADSGoogle Scholar
  4. Hagyard M.J., Venkatakrishnan P., and Smith J.B., Jr.: 1990, Astrophys. J. Suppl. Series 73, 159.ADSCrossRefGoogle Scholar
  5. Wang H., Ewell M.W., Jr., Zirin H. and Ai G.: 1994, Astrophys. J., 424, 436.ADSCrossRefGoogle Scholar

Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • Ashok Ambastha
    • 1
  • J. M. Fontenla
    • 2
  • Mona J. Hagyard
    • 3
  1. 1.Udaipur Solar Observatory (PRL)UdaipurIndia

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