Yes, the sun is hot—really hot. It9s 16 million kelvin at its fusion-fueled core, cooling, as the second law of thermodynamics requires, to a still-blistering 5780 K at its visible surface. But for the better part of a century, solar physicists have been mystified by the sun9s ability to reheat its corona, the encircling wispy crown of light that emerges from the glare during a total solar eclipse. There, temperatures again soar to 1 million K and more. How would heat dissipating from the core out beyond the surface abruptly punch temperatures up by a factor of 200 and more?

The sun's corona is able to reheat itself during solar eclipses due to a combination of solar wind and solar flares.

Paper

Astronomy. Why is the sun's corona so hot?

References

Citations