(r_i, \theta_j)$ are provided on the meridional plane. If $E_{||}$ is larger than the critical value $E_{\mathrm {cr}}$, $\alpha |E_{||}(\boldsymbol{r}_{i,j})| / E_{\mathrm {cr}}$ pairs whose initial velocities are zero are generated in the grid spaces. Here the multiplicity $\alpha$ is set to $\alpha = 2$ and $E_{\mathrm {cr}} = 0.25 B_{\mathrm L}$, where $B_{\mathrm L} = \mu/R_{\mathrm L}^3$ is the light cylinder magnetic field, in the present simulation.

The volume of the grid spaces is in proportion to $r^{-2}$, so that pair creation rate per unit volume is in proportion to $r^{^2}$. This reproduces the fact that the density of target photons supplied from the stellar surface decreases in proportion to $r^{2}$. A time interval for the pair creation is also the parameter of the calculation. In the present calculation, it is such that pairs are created $\sim 75$ times in a rotation period.

The outer boundary is located at 10 $R_{\mathrm L}$. Magnetospheric plasmas are expressed as super-particles, and therefore the exaggerated electric force causes a bound motion like positronium. We remove such bound pairs because they behave as if they were a neutral particle, and they would not affect the structure of the magnetosphere. In the steady state, 