The work is aimed at studying the dynamics of the total electric current and its vertical and horizontal components in active regions (ARs) with different levels of flare activity. The electric current was calculated using Helioseismic and Magnetic Imager (HMI/SDO) data on the spatial distribution of the magnetic field vector components in the photosphere. 73 ARs observed in Cycle 24 were studied. Monitoring of each AR was carried out within ±35° relative to the central solar meridian, which corresponds to a time interval of 3–5 days. A number of features were identified in the behavior of the AR electric currents. In particular, it was shown that: 1) The absolute value of the total electric current density in most of the cases considered is determined by the horizontal electric current, which has a density 1.5–4.5 times higher than that of the vertical electric current. 2) In nine active regions (12% of all ARs analyzed), time intervals were identified when the mean unsigned density of the vertical electric current was approximately equal to or higher than the mean unsigned density of the horizontal electric current. 3) In ARs NOAA 11158 and 12673, in which an additional emergence of the magnetic flux was recorded during the monitoring period, an increase in the vertical, horizontal, and total electric currents occurred 18–20 hours before the first solar flares of high X-ray classes appeared. The growth time of the electric current parameters is significantly less than the growth time of the total unsigned magnetic flux of AR. 4) The highest absolute values of the total electric current density were recorded in ARs with a medium solar flare activity.
Yu. A. Fursyak (Wed,) studied this question.