At https://phys.org/news/2020-04-images-reveal-fine-threads-million-degree…. … researchers at the University of central Lancashire unveil the highest ever resolution images of the Sun – and provide a clue on what it shows. Its outer layer is filled with incredibly fine magnetic threads which are themselves filled with extremely hot million degrees plasma. The ultra sharp images were taken by NASAs High Resolution Coronal Imager. It can pick out structures in the Sun's atmosphere as small as 70km in size – or 0.01% of the Sun's surface. However, the exact physical mechanism that is creating these hot strands is yet to be determined
… see also https://doi.org/10.3847/1538-4357/ab6def