A Large-Scale Electric Current as One of the Sources of Solar Coronal Heating

Abstract

The purpose of this work was to study maps of the temperature distribution in the corona above the NOAA active region (AR) 12 192 outside solar flares and during individual flare events of high X-ray classes as well as to determine the role of electric currents in heating the coronal matter. Data on the distribution of magnetic field vector components in the photosphere provided by the Helioseismic and Magnetic Imager (HMI) instrument on board the Solar Dynamics Observatory (SDO) are used to detect the large-scale electric current and calculate its magnitude. Photogeliograms of the solar corona in ultraviolet (UV) channels 131, 171, 193, and 211 Å provided by the Atmospheric Imaging Assembly (AIA/SDO) instrument are used to estimate the temperature in the corona above active regions (ARs). The following results have been obtained: (1) Outside the time of solar flares, a coronal structure with a temperature of 10 MK or more, which was observed for the entire time interval of AR monitoring and marked the location of a large-scale electric current channel at coronal heights, is detected in the central part above the studied AR. (2) The existence of the high-temperature coronal structure over a long time interval indicates a stationary mode of coronal matter heating due to the ohmic dissipation of large-scale electric currents. (3) It is shown that effective stationary heating of coronal matter by electric currents requires anomalous values of plasma conductivity (σ = 10¹⁰ s^–1) and filamentation of the current channel into elements with a cross section of the order of 10⁸ cm or less. (4) Heating of a coronal loop (loop system) with a cross section of 10⁸ cm and a length of 10¹⁰ cm to a temperature of 10 MK on time scales of a few hours can be implemented under the condition of anomalous plasma conductivity by an electric current in the corona of the order of 10⁹ A. (5) During solar flare events, a decrease (in percentage terms) in the role of electric currents in the processes of coronal matter heating and the activation of additional heating mechanisms are observed.