Plasma anisotropy around a dust particle placed in an external electric field

A self-consistent model of plasma polarization around an isolated micron-sized dust particle under the action of an external electric field is presented. It is shown that the quasineutral condition is fulfilled and the formed volume charge totally screens the dust particle. The ion focusing and wake formation behind the dust particle are demonstrated for different ion mean free paths and the external electric fields. It is obtained that at low values of the external electric field the trapped ions play the main role in the screening of the dust particle charge. For high external electric fields, the density of trapped ions decreases and the dust particle is screened mainly by the free ions.

Figure 1

Electric potential $U(\rho =0,z)-\tilde{E}z$ in the presence of an external electric field.

Figure 2

Dimensionless dust particle charge in the absence of an external electric field for different ion mean free paths $\overline{l_i}$ and dust particle radii $r_0$. Experimental results are presented in Ref. [25] for the particle with radius $0.6\mu \mathrm{m}$.

Figure 3

Bulk charge density $n(\rho =0,z)$ for electrons and different kinds of ions for $E_{\text{eff}}=0$ and $\overline{l_i}/{\lambda }_i=5$. Solid lines show the results obtained in previous work [47].

Figure 4

Functions (a) $n_0\left(r\right)r^2$ and (b) $n_1\left(r\right)r^3$ for $\overline{l_i}/{\lambda }_i=5$ and different values of $E_{\text{eff}}$. The solid line indicates the Debye approximation function.

Figure 5

Functions $n_k\left(r\right)r^2$ for $\overline{l_i}/{\lambda }_i=5$: (a) $E_{\text{eff}}=0.75$ and (b) $E_{\text{eff}}=3.0$.

Figure 6

Function $n_0\left(r\right)r^2$ for $\overline{l_i}/{\lambda }_i=5$: (a) $E_{\text{eff}}=0.0$ and (b) $E_{\text{eff}}=6.0$ for different sorts of ions.

Figure 7

Dependence of dimensionless charges $z_{\text{pl}}$ and $\tilde{z}$ from dimensionless electric field $\tilde{E}$ for $\overline{l_i}/{\lambda }_i=5$ and different particle radii.

Figure 8

Electric potentials $U(\rho =0,z)$ for (a) $r_0=1\mu$ and (b) $r_0=2\mu$, $\overline{l_i}/{\lambda }_i=5$, and different values of $E_{\text{eff}}$.

Figure 9

Dependence of positive peak maximum $U_{max}(z,\theta =0)$ of $\tilde{E}$ for different $r_0$.