Magnetic Connections across the Chromosphere–Corona Transition Region

The plasma contributing to emission from the Sun between cool chromosphere ($\le 10^4$K) and hot corona ($\ge 10^6$K) has been subjected many different interpretations. Here we look at magnetic structure of this transition region (TR) plasma, based upon implications CLASP2 data an active recently published by Ishikawa et al., earlier IRIS SDO quiet regions. al. found that large areas sunspot plages are magnetically unipolar as measured in cores \ion{Mg}{2} resonance lines, formed lower under low plasma-$\beta$ conditions. show images line have fibrils which well aligned with overlying coronal loop segments seen 171 \AA{} channel SDO. When TR regions arise thermally connected corona, then can provide first credible boundary conditions for force-free calculations extended corona. We also re-examine dynamic loops previously reported a major contributor Sun. Dynamic contribute only small fraction total