Cooling Outwards from Corona

Dear fifa1022, you have asked one of the most profound questions confronting solar physicists for many decades.

This big question and several others are directly addressed in the 2012 NRC Solar/Space Physics Decadal Report on recent discoveries and the 10 year agenda for resolving the big questions.
Here is the pertinent Chapter 10 of the report: http://www.nap.edu/openbook.php?record_id=13060&page=257

Respectfully submitted,
Steve

 

It's also an amazingly complicated problem because the gas is so thin. If you have two thick gases next to each other, the energy transfer problem is pretty simple. Stuff moves from hot to cold and the distribution of velocities follows a nice simple pattern called a thermal distribution.

If the gas is very thin, then there isn't time for the gas to move toward a standard distribution of velocities and things can get very, very complicated.