[mesa-users] Radiative-Convective boundary discrepancy

[Momchil Molnar]

Dear All,

I am writing with the following concern - after encountering an 
unexpected behaviour of the Brunt frequency around the 
radiative-convective boundary for a Solar model and sending an email to 
the list, I continued looking through my results and found that the 
Brunt becomes less and less well defined in this region as spatial 
resolution increases (i.e. increase in number of grid points).

I am attaching plots of the Brunt frequency squared for different number 
of grid points for a solar model, evolved from the integrated one in 
/*mesa*//*/star/test_suite/solar_calibration/solar_calibration_input.mod*/, 
using the same inlist differing only in the mesh_delta_coeff 
(accordingly 1 for 1500 model; 0.15 for ~10000 pts model and 0.08 for 
~20000 pts model).

The previous reply, which I received on the topic was leading in a 
direction, which suggests that the boundary layer is very thin and using 
higher resolution models will constrain the inconsistency of the Brunt 
frequency only in a near-by area around the transition region. However, 
as we see, there is an unexpected bump inside of the radiation zone for 
the models with higher spatial resolution, further away from the 
radiative-convective boundary.

Do you think this can be avoided by using different parameters for 
describing the convection mechanism or this might be an implementation 
problem in MESA?

Cheers,
Momchil Molnar
MIT
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