[FLASH-USERS] Magnetic Fields

[John ZuHone]

Hi Malia,

The reference to these as “per volume” fields is a directive to the code more than anything else so it knows how to handle these fields when doing things on the mesh like restricting and prolonging to different refinement levels, filling guardcells, etc. It doesn’t mean that the variables themselves have units of gauss per grid volume, and they do not. 

So if you set UnitSystem=“cgs” that means that the units of those fields should be gauss, and the units of the “magp” variable are erg/cm**3.

Best,

John

> On Apr 18, 2018, at 3:45 PM, Jenks, Malia T. <mjenks at ou.edu> wrote:
> 
> I am using the MHD staggered mesh solver, and Flash 4.4. I saw in the documentation that the magx, magy, magz are per volume. In Simulation_initBlock.F90 I set the magnetic fields I want given in units of Gauss per grid volume. I have UnitSystem set to "CGS". The saved magp from my plot output files is small, it seems to still have the per volume in it. This is also causing the total magnetic energy of my simulation to be small. 
> Should I be initializing magx, magy, and magz in terms of G/volume?
> Do I need to remove the (/volume)^2 from the magp to have a value in terms of energy density?
> 
> Malia Jenks

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