[Mesa-users] New User Seeking Guidance on Downloading and Using MESA Software

[Wafa Gull]

Dear MESA Community,
I hope this message finds you well. My name is Wafa Gull, and I am new to using MESA (Modules for Experiments in Stellar Astrophysics). I am excited to learn more about stellar modeling and to explore the capabilities of MESA for my studies/research.
Could someone kindly guide me on where to download the latest version of MESA and any recommended resources or tutorials for beginners? I am particularly interested in understanding the setup process, initial configuration, and best practices for running my first simulations. Any advice on how to navigate the documentation or suggestions for initial projects would also be greatly appreciated.
I am currently working on the variable stars, more specifically cepheid variable stars.
Thank you very much for your time and help. I look forward to becoming a part of this community and learning from the collective expertise here.
Warm regards,
Wafa Gull
Department of Physics and Astronomy,
The University of Southern Mississippi.


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From: Mesa-users <mesa-users-bounces at lists.mesastar.org> on behalf of Farag, Ebraheem via Mesa-users <mesa-users at lists.mesastar.org>
Sent: Wednesday, November 6, 2024 8:41 PM
To: mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>; Joergensen, Johannes Holm <Johannes.Joergensen at uibk.ac.at>
Subject: Re: [Mesa-users] Convergence issues solved by changing a_mlt


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Hello Johannes,

> For context, I am running some "complicated" accreting pre-MS models with the framework developed by Steindl+ 2022.

Very cool! Thomas did some nice work on developing a framework for pre-MS accretion.

> From examining the output of the solver I see that the issues arise in convection zones. By trial and error I solved a lot of my convergence issues by simply changing the mixing length parameter slightly (e.g. from 1.9 to 1.85). My question is: Is there any way to interpret this? My models show interesting interiors with often many tiny convection cells which I imagine are difficult to handle; could a change in a_mlt help in this regard?

If I'm understanding correctly, by decreasing 'alpha_mlt' from 'alpha_mlt = 1.9' to 'alpha_mlt = 1.85', you were able to solver most of your convergence issues?

if decreasing alpha_mlt is indeed solving your issue, are these problematic convective zones becoming radiative in the improved working model? Naively, I would imagine the problem would become worse with lower alpha_mlt unless the zone becomes entirely radiative.

I think two plots could help in diagnosing what's happening.

1- logT vs logRho profile of the whole model (a pgstar will work well, and it shows where convection operates along the profile)
2- superadiabicity (∇−∇ad) vs logT (so we can match the superadiabatic regions with regions in trho profile)

If you can answer these questions, I can attempt to provide an explanation.

-EbF





________________________________
From: Mesa-users <mesa-users-bounces at lists.mesastar.org> on behalf of Joergensen, Johannes Holm via Mesa-users <mesa-users at lists.mesastar.org>
Sent: Wednesday, November 6, 2024 4:50 AM
To: mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>
Subject: [Mesa-users] Convergence issues solved by changing a_mlt


Hi everyone,


I am having convergence issues in MESA. For context, I am running some "complicated" accreting pre-MS models with the framework developed by Steindl+ 2022. From examining the output of the solver I see that the issues arise in convection zones. By trial and error I solved a lot of my convergence issues by simply changing the mixing length parameter slightly (e.g. from 1.9 to 1.85). My question is: Is there any way to interpret this? My models show interesting interiors with often many tiny convection cells which I imagine are difficult to handle; could a change in a_mlt help in this regard? I would gladly provide figures that showcase this, or my inlists. Much gratitude for any help!

Cheers, Johannes
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