Authors: Melissa Bierschenk (GMU), Jie Zhang (GMU), Suman Dhakal (GMU), Jake Serna (GMU), Eleni Nikou (US NRL)

Polarity inversion lines (PILs) of solar active regions (ARs) are key sites where non-potential magnetic energy accumulates, often leading to the materialization of eruptive magnetic structures, which are the main drivers of space weather. The formation of such critical regions is theorized by two main ideas. One is the emergence of a current-carrying magnetic flux tube with exceptional twist. Another idea is that the converging and shearing motions of positive and negative fluxes from nonconjugate poles (opposite magnetic polarities that did not originate from the same emerging bipole) are the main causes of a compact, or strong-gradient, PIL. The Daniel K. Inouye Solar Telescope (DKIST), with its uniquely high spatial resolution, offers an unprecedented opportunity to examine such a region in finer detail. This study uses spectropolarimetric observations from the Visible Spectro–Polarimeter (ViSP) instrument on DKIST, collected under proposal ID pid_2_114. We apply Milne-Eddington approximations to the photospheric Fe I line doublet. The detailed 3-D vector fields surrounding the PIL are revealed. Around the PIL region, the total field is the strongest, and the dominating horizontal fields are nearly parallel with the PIL throughout the entire length. Most importantly, there is a presence of strong downflow along a narrow region along the PIL. These observational results strongly suggest that the strong-gradient PIL regions are produced by the process of collisional shearing.