Hell is the sun?

[Angrboda]

Which is hotter the core or the surface of the sun?
The core is something like 15 million degrees C, and the corona is at something like 2 to 4 million degrees. The corona is hotter than the surface of the sun, but not as hot as the core (where thermonuclear fusion reactions are taking place,which keep the sun "alive").

Why the corona is hotter than the surface of the sun is still an unsolved mystery.