[mesa-users] A thought about the implementation of Solberg-Høilang in MESA

[Richard Townsend]

Hi folks —

I’ve been looking at how MESA implements the SH instability. The code uses a stability criterion based on eqn. (23) of Heger, Langer & Woosley (2000), which involves evaluating the difference between the adiabatic and physical radial density gradients.

But as HLW (2000) point out, eqn. (24) can be written in an alternative form involving temperature gradients — as given in their eqn. 24. On looking at this eqn., it seems that the first term is nothing other than the square of the bouyancy frequency. So, why doesn’t MESA just use N^2 instead of having to numerically difference the two density gradients? Any insights from the community on this?

cheers,

Rich