Influence of the artificial permittivity on particle-in-cell simulation method

Kinetic modeling in many interaction cases between the plasma of not too high density and coupled electro-magnetic fields can be vividly realized by the Particle-In-Cell (PIC) method. It is an effective way to observe most internal details by tracking and advancing individual charged particles step by step within a controlled circumstance. However, it requires huge computation thus leads to a limited application scope. Because of this, several numerical techniques have been proposed and successfully speeded up the whole simulation procedure. By increasing the physical permittivity ε₀ by the square value of an amplification factor γ, both mesh spacing and time step may be largely increased while two basic rules within PIC should always be obeyed thereby γ cannot be exaggerated to the infinite. The numerical test on field solving has shown that with an artificial ε₀ both electric and magnetic fields are reduced by a factor of γ^-2, which may differ from previous analysis but seems consistent to plasma oscillation and wall potential tests. From the simplified modeling on wall potential formation, modified potential with γ=5 has presented even slightly better in comparison with the γ=1 result.