[Mesa-users] Stability Problems with use_other_energy

[José Lopes]

Dear MESA users,

I am developing an extension to MESA to include a Dark Matter Capture framework and interplay with the code. This is all done through the run_star_extras.f and the ‘use_other_energy’ hook. An extra energy contribution is computed for each step (this energy term depends on the stellar structure properties, such has the temperature profile and its second derivative w.r.t. the radius) and is injected as an extra heat term (it can be either positive or negative).

So far most results are consistent with what has already been studied for this phenomenology. The problems however start when the extra energy term grows to the same order of magnitude of either the nuclear energy or gravity energy terms. In these cases, the code shows an irregular oscillatory behavior, almost as if it is unable to converge to a stable solution. 

This oscillatory behavior can be seen in the plots attached to this e-mail (plot1 and plot2). There, you can see the nuclear (black), gravity (red) and extra (blue) energy terms in the first zone (r ~ 0) of the Star, as a function of Model Number. Plot1 shows a case where the extra energy term grows to a magnitude comparable to the nuclear energy term, and plot2 shows a similar situation for the gravity term. I also attach (plot3) a case where the extra energy term is smaller and thus the model is able to converge throughout the evolution, although a glitch can be seen in the gravity
energy term.

I have tried tuning some options in the controls inlist (such has time step control, variable control, mesh-refinement, etc.). However, so far, I have not been able to improve the stability of these models.

As anyone encountered a similar behavior? Is there any control option I should focus on to try and improve stability?

Thank you all,

José Vargas Lopes
PhD Student

CENTRA, Centre for Astrophysics and Gravitation
IST, University of Lisbon, Portugal
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20180316/02772d99/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: plot1.png
Type: image/png
Size: 114788 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20180316/02772d99/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: plot2.png
Type: image/png
Size: 85977 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20180316/02772d99/attachment-0001.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: plot3.png
Type: image/png
Size: 90970 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20180316/02772d99/attachment-0002.png>