Why is the atmosphere of the sun(the corona)hotter than the surface?

Question

The corona is over 1million dgrs.K while the surface is a mere 5800. If core radiation is the culprit then that and convection should push the surface temp. close to that of the corona.

Answer 1

The short answer is that the corona is heated by the whipping and snapping action of magnetic fields on the Sun. This result has been suspected for eons, but recently confirmed with real data.

Answer 2

The magnetic field accelerates the particles.  A changing magnetic field generates and electric field component, and of course it's way too hot for there to be neutral atoms rather than ions.  That raises the question of why that doesn't happen at the photosphere too.  The answer is that it does, but to much less effect.  With the much higher density of the photosphere, there's plenty of charge for the electric field to move.  The resulting currents tend to decrease the electric field (or else electromagnetism would be a perpetual motion machine, and we can't have that).