http://www.sciencemag.org/news/2021/04/solar-campfires-may-heat-sun-s-atmosphere-scorching-temperatures

The Sun, imaged in ultraviolet light by Europe’s Solar Orbiter, revealing the hottest parts of its surface and atmosphere

A new space mission is helping researchers solve one of the most enduring mysteries of our Sun: why its wispy atmosphere is nearly 200 times hotter than the surface below. An analysis of observations made last year by the European-led Solar Orbiter mission, presented today at the European Geosciences Union (EGU) meeting, suggests tiny flares just above the Sun’s surface, dubbed “campfires,” could be enough to heat the atmosphere to its prodigious temperature. Other research at the meeting supports the long-held suspicion that small flares, not large ones, may do most of the heating.