Screening and Attraction of Dust Particles in Plasmas

The potential around a dust particle in a plasma is found using the collisional hydrodynamic equations of dusty plasmas, taking into account ion-dust and ion-neutral collisions and considering the plasma source proportional to the dust density. The linear screening is strongly influenced by the collisions and can substantially differ from Debye screening. Attraction of negatively charged dust particles can occur due to overscreening by the ion fluxes in the presence of friction forces.

Figure 1

Plot of the screening function parameters ${\lambda }_1$, ${\lambda }_2$, $g_1$, and $g_2$ vs $a$ in a linear regime for hydrogen plasma, $\tau =1$, $P_0=0.9$, $z_0=0.843$ (calculated by the charging equation), and $u_e=(z_0/\tau {)}^{1/2}$. The fractional contribution $\rho$ of the term due to the collisions of the ions with the neutrals in ${\alpha }_{dr}$ is also shown (dotted line). The lengths are normalized to the linear Debye radius.

Figure 2

The potential produced by the test dust particle for $a_d/{\lambda }_{D\mathrm{lin}}=0.1$ (normalized to ${10}^{-3}{Z}_{d}e/{\lambda }_{D\mathrm{lin}}$, continuous line) and $a_d/{\lambda }_{D\mathrm{lin}}={10}^{-5}$ (normalized to ${10}^{-5}{Z}_{d}e/{\lambda }_{D\mathrm{lin}}$, dashed line) is compared to the Debye-Hückel potential (normalized to ${10}^{-3}{Z}_{d}e/{\lambda }_{D\mathrm{lin}}$, dotted line). Dusty plasma parameters as in Fig. 1.