[Mesa-users] Unable to change temperature gradient when atomic diffusion is turned on

[Evan Bauer]

Hi Joey,

What MESA version are you using? In 11701 (and other release versions), when diffusion is on, there is a call to update_vars after diffusion updating things to reflect the new composition, but it should also be setting skip_mixing_info = .true. for that call after diffusion. So the lines you've quoted in your email should be skipped for that particular call to update_vars, and diffusion should have no impact on adjust_mlt_gradT_fraction.

There WAS a bug in some dev versions (soon after 15140) that broke some of this logic, but as far as I recall, that bug was fixed fairly promptly and never impacted a release version. So if you're using a dev version, can you point me to the commit number/hash? I should probably be able to help you diagnose a fix.

Cheers,
Evan


> On Aug 23, 2021, at 12:26 PM, Joey Mombarg <joey.mombarg at kuleuven.be> wrote:
> 
> Dear mesa-users,
> 
> I am trying to change the temperature gradient to the adiabatic one in the overshoot zone using the run_star_extras routine from Michielsen et al. 2019, where also atomic diffusion and radiative levitation are turned on. While mesa does indeed report that s% adjust_mlt_gradT_fraction(k) = 1 just before calling adjust_gradT_fraction (around line 668 in star/private/mlt_info.f90, r11701), it seems to be overwritten later in star/private/hydro_vars.f90, around line 565:
> 
>            if (.not. skip_mixing_info) then
>               s% mixing_type(1:nz) = no_mixing
>               s% adjust_mlt_gradT_fraction(1:nz) = -1
>            end if
> 
> This condition seems to be fulfilled during the main-sequence evolution when atomic diffusion is turned on. I was wondering why adjust_mlt_gradT_fraction is changed to -1 here, and if there are any objections in removing this behaviour for this particular case? 
> 
> Kind regards,
> Joey
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