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Signs of Preflare Situation in Solar Ultraviolet and Microwave Emission

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Abstract

The spatial dynamics of microwave emission (data from the Nobeyama Radioheliograph) of active regions with a complex magnetic field configuration before powerful flares, as well as the fine structure of active sources of ultraviolet (UV) emission based on AIA/SDO data, are studied. It is shown that there is unsteady behavior of microwave sources, along with the ignition of a system of crossed UV loops (X-structures). A class-M X-ray flare occurs after several hours at the site of ignition of the intersecting UV loops. The similar behavior observed in microwave and ultraviolet emission in the five active regions studied by us likely serves as a sign of a preflare situation in the active region on the Sun.

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ACKNOWLEDGMENTS

The work was carried out with data from the Nobeyama Radioheliograph, which operates with the assistance of the International Consortium for the Continued Operation of Nobeyama Radioheliograph (ICCON). ICCON includes the ISEE/Nagoya University, the National Astronomical Observatory of China, the Korea Astronomy and Science Institute, the National Institute of Communications and Technology, and the Goddard Space Flight Center of NASA. We are grateful to the SDO team for the observational data from AIA and HMI. A flare catalog is available at the Space Weather Prediction Center of NOAA.

Funding

The work was carried out with the partial support of the Russian Foundation for Basic Research (projects no. 18-02-00856, 17-52-80064) and the Basic Research Program of the Russian Academy of Sciences 12 “Issues of the Origin and Evolution of the Universe.”

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Authors and Affiliations

  1. National Research University Higher School of Economics, Nizhny Novgorod, Russia

    I. A. Bakunina

  2. Central Astronomical Observatory, Russian Academy of Sciences, St. Petersburg, Russia

    V. F. Melnikov

  3. Nizhny Novgorod State University, Nizhny Novgorod, Russia

    A. S. Morgachev

Authors
  1. I. A. Bakunina
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  2. V. F. Melnikov
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  3. A. S. Morgachev
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Correspondence to I. A. Bakunina.

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Bakunina, I.A., Melnikov, V.F. & Morgachev, A.S. Signs of Preflare Situation in Solar Ultraviolet and Microwave Emission. Geomagn. Aeron. 60, 853–859 (2020). https://doi.org/10.1134/S001679322007004X

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