1D2V simulations with electric field switch

[mrhardman]

To support Mantas Abazorius's work, it would be useful to implement a switch to turn off Ez so that the DKE solved for is

$$\frac{\partial F}{\partial t} + v_{\|}\frac{\partial F}{\partial z} = C[F,F]$$

@johnomotani @LucasMontoya4 Where should I implement the switch? Do you agree that this could be an interesting feature?

[LucasMontoya4]

I'm not sure, but maybe it could belong in the composition section of the input file, considering this would be entirely different physics from kinetic or fluid ions? So I guess one of the new flags for ion_physics?

[mrhardman]

I think this is orthogonal to all other options if one just sets a flag that is used in em_fields.jl to set Ez and Er to zero.

[LucasMontoya4]

Sounds much more sensible!

[johnomotani]

I'd be tempted to add this as an electron_physics flag - because electron_physics tells us how to calculate phi and Ez. Could we argue that this switch is equivalent to massless, zero-temperature electrons? So call it something like zero_temperature?

[mrhardman]

I view this as a physics hack for debugging and testing rather than a self-consistent model. The present version of the PR would let you calculate everything everywhere, just with Ez= Er = 0 #269. However, if you are sure that this is a physical limit, then I have no objection to your suggestion to make this as an electron model. Perhaps boltzmann_zero_temperature would make it clear that the electron response must be trivial in this option (if it is a real limit)? @MantasAbazorius What do you think?

[MantasAbazorius]

I think as a physical limit it only makes sense, as John says, if we make electrons massless first, and then take their temperature to zero. So it is a limit in the boltzmann electron approximation and as long as that's clear then it's fine. Otherwise, it's a strange regime, where electron mean flow is larger than their thermal flow and even the negatively charged wall assumption stops making sense.

[mrhardman]

Looking more carefully at the existing code in master, I think that the effect of #269 might be achieved by just setting

[composition]
T_e = 0.0
electron_physics = "boltzmann_electron_response"

@MantasAbazorius if you have a moment to check the output from one of your runs using #269 against an input file where you just set T_e as above, please post here if the results are identical!

[MantasAbazorius]

The ion distribution functions are identical for both T_e=0.0 and the #269 option. When checking the rest of the dynamic data, as expected, mismatches are in data that depends on T_e: electron_thermal_speed, chodura_integral_upper, chodura_integral_lower, electron_parallel_pressure and phi.

[mrhardman]

OK, I will close the PR #269 as redundant. @MantasAbazorius if you make a new install, use master branch from now on, with

[composition]
T_e = 0.0
electron_physics = "boltzmann_electron_response"