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

[Richard Townsend]

> On Sep 28, 2015, at 3:26 PM, Richard Townsend <rhtownsend at icloud.com> wrote:
> 
> As an addendum: looking at eqn. (20) of Maeder, Meynet, Lagarde and Charbonnel (2013), it seems that this is the SH stability criterion expressed using N^2. That is, I think I’m right!
> 

Ah, I in fact meant eqn. 36!

> This leads me to a related question for domain experts: is the SH instability distinct from convection? Or are they two sides of the same coin, since without rotation the SH criterion reduces to the usual convective stability criterion? If the latter, that would suggest that including angular momentum transport and mixing due to (i) convection and (ii) the SH instability will amount to double counting — right?
> 
> cheers,
> 
> Rich
> 
>> On Sep 28, 2015, at 2:54 PM, Richard Townsend <rhtownsend at icloud.com> wrote:
>> 
>> 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
>> 
>