On interior boundaries which are adjacent to both a Plasma Model and Charge Conservation feature, the Surface Charge Accumulation node is used to determine the accumulation of surface charge on the dielectric surface due to incident ion and electron fluxes. This condition should always be applied on boundaries which are adjacent to both a Plasma Model and Charge Conservation feature, otherwise the charged species will “leak” from the modeling domain, resulting in unphysical results. Mathematically, the following boundary condition is implemented:

where ρs is the solution of the following distributed ODE on the boundary:

where n · Ji is the normal component of the total ion current density on the wall and n · Je is the normal component of the total electron current density on the wall. In addition, since the solution is assumed to be time periodic, a periodic boundary condition on the surface charge density is imposed in the extra dimension.