Evolution of photospheric magnetic field and electric currents during the X1.6 Flare in active region NOAA 12192

Abstract

The dynamics of magnetic fields in the Sun’s active regions play a key role in triggering solar eruptions. Studies have shown that changes in the photosphere’s magnetic field can destabilize the large-scale structure of the corona, leading to explosive events such as flares and coronal mass ejections (CMEs). This paper delves into the magnetic field evolution associated with a powerful X1.6 class flare that erupted on October 22, 2014, from the flare-rich active region NOAA 12192. We track these changes using high-resolution vector magnetograms from the Helioseismic and Magnetic Imager (HMI) on NASA’s Solar Dynamic Observatory (SDO). Our analysis reveals that a brightening, a precursor to the flare, began near the newly emerged, small-scale bipolar flux regions. During the X1.6 flare, the magnetic flux in both polarities displayed emergence and cancellation. The total current within the active region peaked during the flare. However, it is a non-CME event, and the ratio of direct-to-return current value remains close to 1. The large flare in this active region occurred when the net current in both polarities attained the same sign. This implies that the Lorentz force, a consequence of the interaction between currents and magnetic fields, would have pushed the field lines together in this scenario. This reconnection of opposing magnetic fields is believed to be the driving force behind the major flare in this active region.