Mystery of sun’s coronal heating
The visible surface of the sun has a temperature of 10,000 degees F. (5,538 degrees C.) One might think that moving away from the inferno would cool things down, but that’s not the case. Instead, the sun’s upper atmosphere, or corona, sizzles at millions of degrees – a temperature 200 to 500 times higher than that of the roaring furnace below.
For more than a half-century, astronomers have tried to figure out what causes the coronal heating. Now, new observations by NASA’s IRIS spacecraft suggest that “heat bombs” are going off in the sun’s outer atmosphere, helping to explain what makes it so mysteriously hot.
Bottom line: NASA video on coronal hearing – why the sun’s outer atmosphere is so mysteriously hot.