On the Role of MHD Turbulence in the Decrease of Electrical Conductivity of Plasma in the Sun’s Active Magnetic Region

Abstract

To overcome the difficulty in effective dissipation of currents in electromagnetic flare models associated with high gas-kinetic conductivity of the solar plasma, attention is given to the possibility of a local decrease in conductivity in the places of highly developed MHD turbulence near the neutral lines of photospheric magnetic configurations. The concept of redistribution of electrical conductivity, which is based on the following physical effects and conditions known from the observations in the solar atmosphere, is proposed: (1) A decrease in the electrical conductivity parameter (increase in the resistivity) in a turbulent medium. (2) Magnetic suppression of turbulence under the influence of strong magnetic fields. (3) Excitation of a large-scale electric field by macroscopic plasma motions in the photosphere in the presence of a magnetic field (photospheric dynamo). (4) The observable spatial inhomogeneous structure of magnetic configurations in the vicinity of sunspot groups, which leads to the formation of current layers with zero (neutral) magnetic fields lines. The calculated values of the MHD-turbulent conductivity near neutral magnetic lines in the photosphere turn out to be almost three orders of magnitude smaller than the values of the regular gas-kinetic conductivity in the places of strong magnetic fields in the vicinity of sunspots. A significantly reduced conductivity in the regions of highly developed MHD turbulence can contribute to accelerated Joule current dissipation, whose energy is consistent with the characteristics of thermal flares.