Proper Use of holmstrom_vacuum_region and n_floor in HybridPIC

[yanghf263]

When using the holmstrom_vacuum_region option in HybridPICSolver, I found that the activation of holmstrom_vacuum_region must be used in conjunction with the setting of n_floor. Could someone please check if my understanding below is correct? I would greatly appreciate it.

• When holmstrom_vacuum_region=true and n_floor>0, the calculation of the electric field in the vacuum region (where rho_val < n_floor*q_e) will solve the simplified Generalized Ohm's Law, dropping the Hall and pressure terms but retaining the resistivity term.
• When holmstrom_vacuum_region=false and n_floor>0, the full Generalized Ohm's Law is used everywhere, and n_floor only appears in the denominator as max(rho, n_floor*q_e) to maintain numerical stability.
• When holmstrom_vacuum_region=true but n_floor=0, the vacuum region mechanism is effectively inactive.

Therefore, the activation and effect of holmstrom_vacuum_region depend on the value of n_floor, which determines the "vacuum" region where this mechanism applies. It seems that this relationship is not clearly described in the current documentation.

[roelof-groenewald]

Hi @yanghf263. Your understanding is correct yes. Feel free to create a PR with updates to the documentation to clarify the effect of holstrom_vacuum_region if you would like.

[yanghf263]

Thanks for your suggestion. I’ve created a PR to address it.