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Measurement and analysis of magnetic field variation during a class 2b flare

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Abstract

We report a digital analysis of high-time-resolution videomagnetograms taken during a class 2b flare that occurred at 60° east. The data were obtained at the Big Bear Observatory and calibrated by a Mt. Wilson magnetogram. Changes of weak magnetic fields (less than 100 G) with an amplitude from 30 to 100% have been detected over 55% of the optical flare region, apparently taking place at the initial phase of the flare. Statistical considerations suggest a real flare association with most of these changes.Hα observations show that large changes took place over the footpoints of heavily inclined structures like penumbral fibrils, while smaller changes took place over the plage region. An apparent polarity reversal was found at the feet of erupted fibrils.

Based on force-free field calculations these changes can be reasonably explained as a transformation of the current-carrying fields to potential fields which produced large changes in the field line inclination and rotation.

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Author notes

  1. Katsuo Tanaka

    Present address: Tokyo Astronomical Observatory, Mitaka, Tokyo, Japan

Authors and Affiliations

  1. Big Bear Solar Observatory, Hale Observatories, Carngie Institution of Washington, California Institute of Technology, and Tokyo Astronomical Observatory, U.S.A.

    Katsuo Tanaka

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  1. Katsuo Tanaka
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Visiting Associate, Summer 1977.

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Tanaka, K. Measurement and analysis of magnetic field variation during a class 2b flare. Sol Phys 58, 149–163 (1978). https://doi.org/10.1007/BF00152561

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  • DOI: https://doi.org/10.1007/BF00152561

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