Analysis of the Vertical Current Evolution for the X9.3 Flare on 6 September 2017

In this article, we examine the morphological evolution and current distribution of the X9.3-class flare on 6 September 2017 that occurred in the active region (AR) 12673. We combine the high-resolution observations of the Atmospheric Imaging Assembly (AIA) and Helioseismic Magnetic Imager (HMI) instruments on board the Solar Dynamics Observatory. The vertical current intensity and the soft X-ray flux within the active region showed two peaks, corresponding, respectively, to the X2.2 and X9.3 flares on that day, while the latter constituted a more significant increase. A pair of conjugate current ribbons appeared at the same locations consistent with the two ribbons of the flare. These current ribbons underwent sustained and significant changes during the X9.3 flare eruption. In the early period of the flare, there was a substantial decrease in the area of the current ribbons, resulting in the emergence of a series of high-density small current islands. During the later phase, not only did the area of the currents rapidly increase, but also the flare kernels evolved into two flare bands along the sheared magnetic neutral line in the photosphere. The AIA 1600 Å and 304 Å images revealed that the two ribbons of the X9.3 flare formed from small bright kernels. It was also observed that the positions of the flare kernels closely matched those of the current islands. Based on the vertical current distribution and evolution near the highly sheared core field region during the X9.3 flare, we conclude that this flare eruption should be attributed to tether-cutting magnetic reconnection.