Coronal heating problem

[Sillychris]

The sun's corona is way way hotter than the surface of the sun. (10^6 K vs 6000 K)

This could not be the case if the heat came directly from the sun's surface (second law of thermodynamics)

What do you think is responsible? The two most likely candidates presently are wave heating theory and magnetic reconnection.

[Idobox]

What about simple thermodynamics?

The surface is in a state of thermal equilibrium, and particle energy follow a typical Maxwell-Boltzman curve. Particles in the high end of the spectrum have enough energy to escape the sun's gravity and end up forming either the corona of the solar wind. Because they are the high-end of the spectrum, they are more energetic than the surface, hence hotter.

[Brotoro]

Alfvén waves.

[LLlAMnYP]

What about simple thermodynamics?

The surface is in a state of thermal equilibrium, and particle energy follow a typical Maxwell-Boltzman curve. Particles in the high end of the spectrum have enough energy to escape the sun's gravity and end up forming either the corona of the solar wind. Because they are the high-end of the spectrum, they are more energetic than the surface, hence hotter.

Nah, that's just ludicrous. That fraction of particles would be on the order of e^(-1000000/6000), if you plug in the numbers, then the expected quantity of such energetic particles in the entire sun would be around 10^(-15).

On the other hand, how do you define the temperature of the corona? The mean free path for a particle in a gas is around 1km (for a particle density of 10^15 per cubic meter, as it is in the corona). Accelerated by the sun's electromagnetic field, perhaps? A mean electric field of 0.1 V/m would be enough to impart this kind of energy to an elementary charge over these lengths.

EDIT: The question about defining temperature is rhetoric, of course. I was hinting, that more conventional methods of heat transfer hardly would play a major role in this problem as was stated by the OP.

Edited February 25, 2014 by LLlAMnYP