http://arxiv.org/abs/2211.01911
Flares and coronal mass ejections are powered by magnetic energy stored in coronal electric currents. Here, we explore the nature of coronal currents in observed and model active region (ARs) by studying manifestations of these currents in photospheric vector magnetograms. We employ Gauss’s separation method, recently introduced to the solar physics literature, to partition the photospheric field into three distinct components, each arising from a separate source: (i) currents passing through the photosphere, (ii) currents flowing below it, and (iii) currents flowing above it. We refer to component (iii) as the photospheric imprint of coronal currents. In both AR 10930 and AR 11158, photospheric imprints exhibit large-scale, spatially coherent structures along these regions’ central, sheared polarity inversion lines (PILs) that are consistent with coronal currents flowing horizontally above these PILs, similar to recent findings in AR 12673 by Schuck et al. (2022). We find similar photospheric imprints in a simple model of a non-potential AR with known currents. We find that flare-associated changes in photospheric imprints in AR 11158 accord with earlier reports that near-PIL fields become more horizontal, consistent with the “implosion” scenario. We hypothesize that this evolution effectively shortens, in an overall sense, current-carrying coronal fields, leading to decreased inductive energy (DIE) in the coronal field. We further hypothesize that, in the hours prior to flares, parts of the coronal field slowly expand, in a process we deem coronal inflation (CI) — essentially, the inverse of the implosion process. Both of these hypotheses are testable with non-potential coronal field extrapolations.
B. Welsch
Fri, 4 Nov 22
8/84
Comments: 28 pages, 10 figures, to be submitted to ApJ