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Flares and coronal mass ejections are powered by magnetic energy stored incoronal electric currents. Here, we explore the nature of coronal currents inobserved and model active region (ARs) by studying manifestations of thesecurrents in photospheric vector magnetograms. We employ Gauss's separationmethod, recently introduced to the solar physics literature, to partition thephotospheric field into three distinct components, each arising from a separatesource: (i) currents passing through the photosphere, (ii) currents flowingbelow it, and (iii) currents flowing above it. We refer to component (iii) asthe photospheric imprint of coronal currents. In both AR 10930 and AR 11158,photospheric imprints exhibit large-scale, spatially coherent structures alongthese regions' central, sheared polarity inversion lines (PILs) that areconsistent with coronal currents flowing horizontally above these PILs, similarto recent findings in AR 12673 by Schuck et al. (2022). We find similarphotospheric imprints in a simple model of a non-potential AR with knowncurrents. We find that flare-associated changes in photospheric imprints in AR11158 accord with earlier reports that near-PIL fields become more horizontal,consistent with the "implosion" scenario. We hypothesize that this evolutioneffectively shortens, in an overall sense, current-carrying coronal fields,leading to decreased inductive energy (DIE) in the coronal field. We furtherhypothesize that, in the hours prior to flares, parts of the coronal fieldslowly expand, in a process we deem coronal inflation (CI) -- essentially, theinverse of the implosion process. Both of these hypotheses are testable withnon-potential coronal field extrapolations.

The Photospheric Imprints of Coronal Electric Currents