current and species current

[feelingxxxxxxx]

Hi,
I set the output of J_z in the input.deck，as shown in the first figure. However, when I read the sdf of J_z by Matlab, I find the J_z not equal J_{iz}-J_{ez}，and J_z not equal J_{iz}+J_{ez}, and J_z not equal J_{ez}-J_{iz}. So, what do the J_z, J_{iz} and J_{ez} represent respectively in the second picture，and what is the relationship between them？

[Status-Mirror]

Hi @feelingxxxxxxx,

I think the code uses two different methods to calculate the total current density, and the particle-specific current density.

For the total, we look at the macro-particle shapes in each cell before and after the push. From the change in cell-weighting, we deduce the current-flow. This has the effect of being charge-conserving.

For the by-species current, we take the instantaneous momentum of each macro-particle, and calculate its current from the product of its charge density and speed. This is then written to the grid using the macro-particle shape. This is a slightly different operation, as it doesn't take into account the changing weights in each cell over a step.

So the results won't be exactly the same, but they should still be very close. Are you finding the currents to be radically different?

Cheers,
Stuart

[feelingxxxxxxx]

Hi @Status-Mirror ,
Thank you for your reply. I have drawn the total current density and the species' current density, which are slightly different. So, if we need to use the current density data, do you have any good ideas about how to deal with them?