[Mesa-users] first dredge-up suppressed by thermohaline mixing at high spatial resolution?

[Cao, Kaili]

Dear MESA Users,

Recently, I did a series of numerical convergence tests following MESA test case 1M_thermohaline using r22.11.1. (Thanks to Meridith Joyce who told me better ways to model thermohaline mixing, but we have decided to start with the test case.)

The first dredge-up, which causes surface C and N abundances to change as stars climb up the first-ascent red giant branch, seems to be suppressed by thermohaline mixing at high spatial resolution (small mesh_delta_coeff). As shown in attached plots, when this coefficient is set to 0.6 or 0.8, the degree of FDU is significantly reduced; when it is set to 0.2 or 0.4, the FDU almost does not happen.

I can share full inlists if needed, but I think the following lines are the most important:
      use_Ledoux_criterion = .true.
      thermohaline_coeff = 1
      thermohaline_option = 'Brown_Garaud_Stellmach_13'
      varcontrol_target = 1d-4

Has anyone seen this before and figured out a workaround? Thanks a lot.

Cheers,
Kaili


[cid:1cbcb725-105b-49aa-b0df-f4e7b9e79436]
[cid:a6254ee9-769f-4bde-b6be-36fc56c83e75]
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