[Mesa-users] Overshooting in MESA

[Radek Smolec]

Dear Jelena,

wt., 22 mar 2022 o 11:55 Jelena Petrović <jpetrovic at aob.rs> napisał(a):

> Dear all,
>
> Could you please let me know how to switch on overshooting in my MESA
> models (massive stars in range 30 to 40 Ms)?
> I need to use r10398 version, as I should compare results with my old
> models made with this version.
>
> I assume default models do not include overshooting at all.. Is that
> correct?
> Some parameters in controls.defaults are not zero, such as:
> min_overshoot_q = 1d-3
> D_mix_ov_limit = 1d2
> Is there maybe some minimal overshooting included by default?
>
By default there is no overshooting. As you may see in
$MESA_DIR/star/defaults/controls.default
the above controls do not set the extent of overshooting. Please make sure
that you look at controls.defaults for the version that you are actually
using, see below.


> There are various parameters such as:
> overshoot_scheme(:) = '' ! ``exponential``, ``step``, ``other``
> overshoot_zone_type(:) = '' !  ``burn_H``, ``burn_He``, ``burn_Z``,
> ``nonburn``, ``any``
> overshoot_zone_loc(:) = '' ! ``core``, ``shell``, ``any``
> overshoot_bdy_loc(:) = '' ! ``bottom``, ``top``, ``any``
>
> Since I need to calculate helium core masses, I guess I should choose
> 'step', 'burn H', 'core' and 'top'?
>

The above settings just indicate where overshooting should be applied and
what scheme should be used (step overshooting at the edge of the
hydrogen-burning core).
But these controls are not available in 10398. Instead, there are controls
that set the extent of overshooting for a given boundary, like:
         step_overshoot_f_above_burn_h_core = 0
         step_overshoot_f0_above_burn_h_core = 0
for step overshooting, and:
         overshoot_f_above_burn_h_core = 0
         overshoot_f0_above_burn_h_core = -1
for exponential scheme.

Note that you need to set both f and f0 controls - their meaning is nicely
explained in controls.default.

Let me note that for your problem the scheme for determining the location
of convective boundaries may also be important (in 10398 predictive mixing
is available, see 4th MESA instrument paper)
Best wishes,
Radek


I am also not sure what else do I need to include and what values should
> be used for:
> overshoot_f(:) = 0d0
> overshoot_f0(:) = 0d0
>



> Many thanks!
> Jelena
>
>
>
>
>
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