[FLASH-USERS] How to add an implicit solver of magnetic diffusion process

[Zhang Daoyuan]

Hi!

 

I want to ask that how to add an implicit solver of magnetic diffusion in FLASH. FLASH use an explicit solver of magnetic diffusion. However, it is not very good because we need to set an extremely high resistivity for vacuum in simulation so that the time step will be very small. We need an implicit solver of magnetic diffusion if there is the magnetic field and vacuum in simulation.

 

It seems that there is a general implicit solver and the implicit solver for thermal conduction and radiation diffusion. I think it is not difficult for FLASH because the implicit solver for magnetic diffusion is very similar to thermal conduction if we ignore the Hall effect and Biemann Battery. And in previous answer, Ryan Faber has mentioned that:

 

“In addition to guaranteeing stability with modifications to the timestep limiter, you can try using a non-explicit solver. The Townsend solver is pretty easy to implement and quite stable: https://iopscience.iop.org/article/10.1088/0067-0049/181/2/391/meta”

 

It seems that we can add an implicit solver in FLASH.

 

Is there anybody told me what should I do if I want to add an implicit solver for magnetic diffusion?  Thank you very much!

 

Yours

Zhang
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