Comment by jauntywundrkind

At sea-level there can be 1.225 kg/m^3 of particles. There's a lot of matter to absorb heat.

In the exosphere we have 1e-13 kg/m^3 of particles.

My point is that the exosphere while huge has an incredibly tiny thermal battery. I'm not convinced that, were we able to dump heat into it, that it really would be insignificant heating over time.

And there's little way for the articles here to cool down. There's no matter to transfer their energy to.

I guess the thing is, it doesn't matter. It seems like the exosphere is actually already >500 degrees: that after you leave the 80km menopause temperatures soar quickly, in what scant air is left. I was still using a model of thermal transfer. But the only cooling possible is passive radiative cooling, is to glow your energy away. Some of this will find other exospheric particles to hit & excite more, but they're already incredibly energetic up there, and there's just not many particles at all, so perhaps a lot of that radiation might escape the exosphere without collision. Again my mistake: thermal transfer is simply not that relevant (aside some shielding against these particles in vulnerable spots), it's all passive radiation being used to cool.

It would still be interesting to me to have some guestimates for what the current energy balance of the exosphere is. What is heating it, how much, and where/how-much is it able to dissipate its energy?