Study of the physical mechanism of a solar flare using MHD modeling over an active region: the onset of an extended surface of magnetic lines passing through a chain of current density maxima

The primary release of solar flare energy in the corona at altitudes of 15,000 — 70,000 km is explained by the physical mechanism of S.I. Syrovatsky, based on the rapid release of energy accumulated in the magnetic field of the current layer. The observed manifestations of the solar flare are explained by its electrodynamic model proposed by I.M. Podgorny. The model uses analogies with the electrodynamic model of a substorm, previously developed by its author. Since it is impossible to obtain the magnetic field configuration in the corona from observations, it is necessary to conduct MHD modeling. When setting the problem, no assumptions were made about the mechanism of the solar flare. For the numerical solution, an upwind absolutely implicit finite-difference scheme, conservative with respect to magnetic flux, was developed. The scheme is realized in the PERESVET computer program. A detailed study of the pre-flare state over the active region AR 10365 was conducted. The study revealed the emergence of an extended current sheet 50,000 km wide, which is a surface of magnetic lines passing through a chain of closely spaced current density maxima. The magnetic lines of the surface are in the form of arches located in the bright region of the flare emission. At the center of such a current sheet, a 3D maximum of current density does not necessarily have to be achieved. An appearance of a flare in such an arcade is explained by the fact that the main part of the surface of the magnetic arcs has properties that contribute to the development of flare instability.