General Question AtmGamma??

[jedidia]

There is an atmospheric parameter in the planet config, called AtmGamma. The manual explains it as "ratio of specific heats Cp / Cv". The only thing I understand from that explanation is "ratio". I have a faint Idea what speific heat is, and I think Cp ihas something to do with pressure and Cv with volume, but I'm at a total loss how to calculate it.

Say I have an atmosphere of which I know composition, molar constant, surface pressure and maximum and minimum temperature, would that data help to calculate the ratio of specific heats, and how would I have to do that?

 

[kwan3217]

This is something from real gas theory in chemistry. You can basically think of it as a correction factor for the speed of sound formula.

Newton came up with a theory to predict the speed of sound, but it was wrong by a factor of 1.4. It turns out there is a reason for this, something to do with energy being absorbed by the rotation of molecules or something like that. Anyway, there is a hard theoretical explanation for this "fudge factor".

Monatomic gases like helium are supposed to have a gamma of around 5/3 ~1.667, while diatomic gases like most of those in the atmosphere are supposed to have a gamma of 7/5=1.4 . Real gases have to have their gamma measured.

You can see more details on Wikipedia under [ame="http://en.wikipedia.org/wiki/Adiabatic_index"]Heat capacity ratio - Wikipedia, the free encyclopedia[/ame] including a measured table of real gases under real temperature conditions.

 

[jedidia]

thanks for the table, that will come in handy.