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Statistical Study of Solar White-light Flares and Comparison with Superflares on Solar-type Stars

Published online by Cambridge University Press:  27 November 2018

Kosuke Namekata*
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Takahito Sakaue
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Kyoko Watanabe
Affiliation:
National Defense Academy of Japan, 1-10-20 Hashirimizu, Yokosuka, 239-8686, Japan
Ayumi Asai
Affiliation:
Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471, Japan Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471, Japan
Hiroyuki Maehara
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Yuta Notsu
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Shota Notsu
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Satoshi Honda
Affiliation:
Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, Sayo-cho, Sayo-gun, Hyogo, 679-5313, Japan
Takako T. Ishii
Affiliation:
Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471, Japan
Kai Ikuta
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Daisaku Nogami
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Kazunari Shibata
Affiliation:
Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471, Japan Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471, Japan
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Abstract

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Recently, many superflares on solar-type stars were discovered as white-light flares (WLFs). A correlation between the energies (E) and durations (t) of superflares is derived as tE0.39, and this can be theoretically explained by magnetic reconnection (tE1/3). In this study, we carried out a statistical research on 50 solar WLFs with SDO/HMI to examine the t-E relation. As a result, the t-E relation on solar WLFs (tE0.38) is quite similar stellar superflares, but the durations of stellar superflares are much shorter than those extrapolated from solar WLFs. We present the following two interpretations; (1) in solar flares, the cooling timescale of WL emission may be longer than the reconnection one, and the decay time can be determined by the cooling timescale; (2) the distribution can be understood by applying a scaling law tE1/3B−5/3 derived from the magnetic reconnection theory.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2018 

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