[Mesa-users] Brunt-Vaisala frequency is noisy

[Pedro Nuno David Gomes]

A 2018-12-05 19:45, Francis Timmes escreveu:
>> I don't understand why this is happening.
> 
> consider plotting the composition, noting the locations where there are
> sharp abundance gradients, and compare those locations to where the BV 
> spikes.
> do the same for thermodynamic variables such as the density and 
> temperature.
> what do you surmise?
> 
> fxt
> 
> 
> 
> 
>> On Dec 5, 2018, at 10:22 AM, Pedro Nuno David Gomes via Mesa-users 
>> <mesa-users at lists.mesastar.org> wrote:
>> 
>> Dear MESA users,
>> 
>> I'm trying to evolve a 1.5 solar mass star to a point in the red giant 
>> branch. For this model, among other quantities, I need the 
>> Brunt-Vaisala (which from here on I shall call BV) frequency in the 
>> main sequence, subgiant and red giant phases.
>> 
>> The BV determined by MESA is shown to be extremely noisy, and I don't 
>> understand why. I'm sending attached the BV^2 plots for these 3 
>> phases, as well as the inlist I am using. I am using release 10398.
>> 
>> I don't understand why this is happening, so I would be greatly 
>> appreciated if someone could help me solving this problem.
>> 
>> Thank you very much for your attention,
>> 
>> Pedro<BV2_MS.png><BV2_redgiant.png><BV2_subgiant.png><inlist_project_1.5M>_______________________________________________
>> mesa-users at lists.mesastar.org
>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>> 

I followed your advice, and plotted the quantities you mentioned, plus 
dlnRho_dlnR, for a star with a mass of 1.6 solar masses at the end of 
the subgiant branch.

The temperature profile seems normal, but lnRho varies sharply at r = 
0.10 (in units of solar radius). Consequently, dlnRho_dlnR also has a 
sharp variation at this point. I'm assuming this density variation is 
caused by a sharp variation of the helium abundance?... , also in the 
images.

If this is the cause is there anyway to solve it?



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