Electrostatic potential behind a macroparticle in a drifting collisional plasma: Effect of plasma absorption

Abstract

The electric field and potential behind a small absorbing body (dust grain) at floating potential has been calculated analytically in a highly collisional drifting plasma. Linear plasma response formalism has been used and main attention has been focused on the effect of plasma absorption on the grain. It is shown that the long-range asymptote of the electric field is dominated by the effect of absorption and is always negative. Depending on plasma parameters, the electric field at intermediate distances can either increase monotonically or exhibit one maximum and one minimum. It can achieve positive values in certain parameter regimes, which indicates the possibility of electrostatic attraction between the grains aligned parallel to the flow. The obtained results can be important for understanding of the binary grain interactions in complex plasmas at elevated pressures.

Shielding of absorbing objects in collisionless flowing plasma

“…[This result, obtained kinetically for collisionless plasmas, qualitatively agrees with the findings of Chaudhuri et al [13] for the dominant role of absorption in the far-field of grains immersed in strongly collisional drifting plasmas.] The absorption of ions by the grain changes the radial dependance of the far asymptote of the total grain potential from…”

“…The effect of ion-neutral collisions will most probably modify the results obtained here, as the collisions lead to an r −2 tail in the shielding potential of a test (nonabsorbing) grain in drifting plasmas [23,24], and to an r −1 tail in the shielding potential of an absorbing grain in isotropic plasmas [7,25,26] or drifting strongly collisional plasmas [13]. The generalization of the kinetic model with absorption used in this work, to include collisions, and the study of the effect of absorption on shielding of dust grains in flowing plasmas with arbitrary degree of ion-neutral collisionality, are left for future work.…”

“…[13,14]. It was demonstrated that, at least in the case of highly collisional plasmas considered there, the far asymptote of the grain field is dominated by the effect of absorption.…”

“…However, the kinetic model for shielding of grains in anisotropic plasma developed by Ivlev et al [15], does not account for the absorption of ions by the grain. It is thus the aim of the present paper to study, using a kinetic model, the effect of absorption on grain shielding in the limiting case of collisionless flowing plasmas, thus covering the opposite limit of collisionality to that studied in [13,14].…”

“…Appendix A: Derivation of Eq (13) Using dv = v ⊥ dv ⊥ dv dα, the integral in the second term in the right-hand side of (12) can be written as…”