The Astrophysical Journal: Using measurements of photospheric and chromospheric magnetic fields from the GREGOR GRIS instrument, the paper refutes the idea that magnetic reconnection of network magnetic fields with granular fields drives coronal heating. Instead heating arises within primarily unipolar fields above the chromosphere.
Upper panels show measurements of photospheric chromospheric magnetic fields which are unipolar (black contours containing strong magnetic flux), and only very weak fields of opposite polarity far from the unipolar fields (red and blue). The lower panels show emission from overlying transition region and coronal plasma, associated almost completely with unipolar fields far from minority polarity concentrations.