The question of why several kilometers of the solar atmosphere have a temperature 200-500 times higher than the temperature of the solar surface has long remained open. But NASA experts are close to solving the problem.
Life experience tells us that the closer you bring your hand to the flame, the hotter your hand will be. However, in space, many things do not work as everyday experience suggests: for example, the temperature of the visible surface of the Sun is "only" 5800 K (5526.85 ° C), but at a distance, in the outer layers of the star's atmosphere, it rises to millions of degrees.
Try to solve this small particular problem, known as the Problems of heating the solar corona, one of the unsolved problems of modern physics! When the phenomenon was discovered, it seemed to scientists that the solar corona violates the second law of thermodynamics - after all, energy from the inside of the star cannot be transferred to the corona, bypassing the surface.
Before 2007, there were two main theories to explain the heating of the solar corona. One said that magnetic fields accelerate corona plasma to incredible energies, due to which it acquires a temperature above the surface temperature. The authors of the second theory were inclined to believe that energy bursts into the atmosphere from inside the star.
Research by Bart De Pontieu and his colleagues have shown that shock waves emanating from the interior of a star have enough energy to constantly energize the corona.
In 2013, NASA launched the IRIS probe, which continuously captures the boundary between the sun's surface and the corona at different ranges. His goal was to answer the same question: does the solar corona have one constant source of heat, or does energy enter the sun's atmosphere as a result of many explosions? The difference between these two explanations is very large, but it is very difficult to understand which one is correct due to the enormous thermal conductivity of the corona. As soon as an energy release occurs at a particular point on the Sun, the temperature rises almost instantly over a huge area around this point, and it seems that the temperature of the corona is more or less constant.
But the IRIS device recorded changes in corona temperature with such a small interval that scientists were able to see many "nanoflares" where magnetic lines intersected or superimposed. The question of whether there is a source of thermal radiation that uniformly and constantly heats the corona remains open, but it is now clear that at least some of the energy enters the Sun's atmosphere from the interior of the star as a result of such explosions.
Promotional video:
Later, the IRIS observations were confirmed by the EUNIS apparatus. Scientists are now almost certain that the solar corona is heating up precisely because of the many small explosions that release incandescent plasma into the star's atmosphere, the temperature of which is much higher than the temperature of the sun's surface.