Evidence for a relationship between emerging magnetic fields, electric currents, and solar flares observed on May 10, 2012


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Multi-wavelength observations and magnetic-field data for the solar flare of May 10, 2012 (04: 18 UT) are analyzed. A sign change in the line-of-sight magnetic field in the umbra of a small spot has been detected. This is at least partly associated with the emergence of a new magnetic field. A hard X-ray flare was recorded at almost the same time, and a “sunquake” was generated by the impact of the disturbance in the range of energy release on the photosphere. A sigmoid flare was recorded at the beginning of the event, but did not spread, as it usually does, along the polarity inversion (neutral) line. SDO/HMI full vectormagnetic-fieldmeasurements are used to extrapolate the magnetic field of AR 11476 into the corona, and to derive the distribution of vertical currents jz in the photosphere. The relationship between the distribution of currents in the active region and the occurrence of flares is quite complex. The expected “ideal” behavior of the current system before and after the flare (e.g., described by Sharykin and Kosovichev) is observed only in the sigmoid region. The results obtained are compared with observations of two other flares recorded in this active region on the same day, one similar to the discussed flare and the other different. The results confirm that the formation and eruption of large-scale magnetic flux ropes in sigmoid flares is associated with shear motions in the photosphere, the emergence of twisted magnetic tubes, and the subsequent development of the torus instability.

作者简介

M. Livshits

Pushkov Institute of Terrestrial Magnetism, the Ionosphere and Radio Wave Propagation

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Email: maliv@mail.ru
俄罗斯联邦, Troitsk, Moscow

I. Grigoryeva

Central (Pulkovo) Astronomical Observatory

Email: maliv@mail.ru
俄罗斯联邦, Pulkovo, St. Petersburg

I. Myshyakov

Institute of Solar–Terrestrial Physics, Siberian Branch

Email: maliv@mail.ru
俄罗斯联邦, Irkutsk

G. Rudenko

Institute of Solar–Terrestrial Physics, Siberian Branch

Email: maliv@mail.ru
俄罗斯联邦, Irkutsk

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