Are the particle velocities that are being measure correlated at all? As in, flowing away from the sun or similar? I'd think that something with a well-defined "temperature" would be composed of randomly moving particles with a mean velocity of zero. I'd also be interested in the distribution of particle speeds. Would anyone one consider a collimated beam of neutrons to have a temperature?
And I wonder what the distance mean free path length is. I suppose that must be pretty large. So that the T^4 Boltzmann radiation law doesn't really apply to these ~40,000 Kelvin temperatures? Or maybe the emissivity of hard vacuum is really low? I guess I've never thought about it before.