Publication: ApJ; HAO Author: Philip Judge
Edge-enhanced images from near the core of the Mg II k line (left panel, from an IRIS raster on 2019 April 11 from 15:57:54 to 16:25:26 UT) and in the AIA 171 Angstrom channel (right panel, 16:53:33 UT) are shown. The images are from times close to the CLASP2 observations. The central part of these images is all of the same magnetic polarity as measured using CLASP2 data by Ishikawa et al. (2021) in the Mg II lines.
The bulk of the emission from the plasma called "transition region" plasma originates from structures energetically connected both to the chromosphere and corona. This result resolves decades of debate and opens the door to measuring magnetic energy and its evolution in the corona using transition region emission lines.