[mesa-users] Issues with Atmosphere at very low tau

[Ehsan Moravveji]

Hello everyone.

I am looking into how the atmosphere is sampled when we include it to the model, and specifically for a later use in the GYRE.
I would like to stretch the atmosphere to log_tau = -7.

1. Among all possibilities available with which_atm_option, only the two T-tau schemes (i.e. Eddington_grey and Krishna-Swamy) do not crash. The rest end up with convergence problem.
I know that I'm really pushing it beyond the ordinary limit.
So, I would really like to be able to get the Paczynski_grey and grey_and_kap to work, but do not know where to start.

2. When I plot the temperature profile, I notice that the outer atmosphere is poorly sampled.
This is for a 10Msun main sequence star.
Please take a look at the attached plot. The green line is shifted up for better visibility.
There exists only and only one point above log_tau~ -3.0 and it is at log_tau=-7.0 (where I put my top of atmosphere).
To overcome this, I tried to put some T-dependent weight on the meshing:

      use_other_mesh_functions = .true.

      ! temperature gradient
      ! T_function1 = T_function1_weight*log10(T)
    T_function1_weight = 110
      ! T_function2 = T_function2_weight*log10(T / (T + T_function2_param))
    T_function2_weight = 500
    T_function2_param = 2d4 
       ! largest change in T_function2 happens around this temperature
       ! default value puts this in the envelope ionization region.
       
but it simply does not give my any improvement.
Do you guys have any idea how to tackle these two issues?

I have attached the inlist and a model to load from.
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Thanks.
Ehsan.
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