[FLASH-USERS] About (fully ionised) electrons+ions mhd simulations in flash

[Marissa B. P. Adams]

Hi Ernesto,

The short answer: no.

More explanation: FLASH advances the total momentum equation for the
system; therefore everything is treated as a single fluid, however that
fluid is composed of three "species" (in flash terms) as you have pointed
out via the 3T treatment. There are other codes that follow a comparable
prescription with two-temperatures, such as GORGON (see the thesis by
Benjamin Khiar). I would recommend looking at 14.3+ of the user manual (you
probably have already). Long story short 3T/2T =/= 2-fluid.

Aside: One can then make the approximation that given the ions are 43 times
heavier than the electrons for even the lightest element (Z=1) that this is
a fine assumption, and one can fold in the electron equation of motion into
the induction equation that advances the Generalized Ohm's Law. I am not
stating that this is what single-fluid MHD codes with x-MHD
capabilities "do," but it is one perspective of viewing the single-fluid
treatment if albeit physically flawed.

I hope this helps, or at least clarifies/makes some sense :)

Have a nice day!
Marissa

On Mon, Feb 14, 2022 at 11:20 AM Ernesto Zurbriggen <ezurbriggen at unc.edu.ar>
wrote:

> Hello everyone.
>
> I wonder if it is possible to perform 2-fluids (fully ionised plasma, i.e.
> electrons+ions) mhd simulations in flash using the unsplit staggered mesh
> solver.
>
> In the user manual I saw flash allows unsplit hydrodynamic +
> 3-temperatures (electron, ions, radiation), but I'm not sure if this is the
> same or customisable to a strict 2-fluid MHD scenario.
>
> Any information would be appreciated.
> Best regards!
> Ernesto.
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Marissa B. P. Adams
(she/her/hers)
Phd Candidate, University of Rochester
*E-mail:* madams at pas.rochester.edu
*Website:* https://www.pas.rochester.edu/~madams
<http://www.pas.rochester.edu/~madams#>
*Current Location:*
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471 Bausch and Lomb Hall
University of Rochester
Rochester, NY 14627
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