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Title: Energy Loss of Test Charges in a Dusty Plasma in the Presence of Dynamical Grain Charging

Abstract

The dynamical charging of dust grains is an important process and is found to enhance the shielding of a test charge passing through a multi-component dusty plasma. In the present work, the energy loss of a test charge projectile passing through a dusty plasma in the presence of dynamical grain charging is studied. The electric forces can be written in terms of the Maxwell stress tensor for a sphere around the test charge. For sphere with radius tending to zero the force is just that on the test charge. For a finite radius, forces on the plasma are also included which makes it possible to see how the force on the test charge is balanced by the force on the plasma. The method fails for the zero radius but the drag force can be found from a simple physical model. The general analytical results are presented and are compared with the previous results.

Authors:
;  [1]
  1. Alfven Laboratory, Division of Plasma Physics, Royal Institute of Technology, SE-100 44, Stockholm (Sweden)
Publication Date:
OSTI Identifier:
20726824
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 799; Journal Issue: 1; Conference: 4. international conference on the physics of dusty plasmas, Orleans (France), 13-17 Jun 2005; Other Information: DOI: 10.1063/1.2134672; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DUSTS; ELECTRIC CHARGES; ELECTRON COLLISIONS; ION COLLISIONS; PARTICLES; PLASMA; SPHERES; STRESSES; TENSORS

Citation Formats

Shafiq, Muhammad, and Raadu, Michael A. Energy Loss of Test Charges in a Dusty Plasma in the Presence of Dynamical Grain Charging. United States: N. p., 2005. Web. doi:10.1063/1.2134672.
Shafiq, Muhammad, & Raadu, Michael A. Energy Loss of Test Charges in a Dusty Plasma in the Presence of Dynamical Grain Charging. United States. doi:10.1063/1.2134672.
Shafiq, Muhammad, and Raadu, Michael A. Mon . "Energy Loss of Test Charges in a Dusty Plasma in the Presence of Dynamical Grain Charging". United States. doi:10.1063/1.2134672.
@article{osti_20726824,
title = {Energy Loss of Test Charges in a Dusty Plasma in the Presence of Dynamical Grain Charging},
author = {Shafiq, Muhammad and Raadu, Michael A.},
abstractNote = {The dynamical charging of dust grains is an important process and is found to enhance the shielding of a test charge passing through a multi-component dusty plasma. In the present work, the energy loss of a test charge projectile passing through a dusty plasma in the presence of dynamical grain charging is studied. The electric forces can be written in terms of the Maxwell stress tensor for a sphere around the test charge. For sphere with radius tending to zero the force is just that on the test charge. For a finite radius, forces on the plasma are also included which makes it possible to see how the force on the test charge is balanced by the force on the plasma. The method fails for the zero radius but the drag force can be found from a simple physical model. The general analytical results are presented and are compared with the previous results.},
doi = {10.1063/1.2134672},
journal = {AIP Conference Proceedings},
number = 1,
volume = 799,
place = {United States},
year = {Mon Oct 31 00:00:00 EST 2005},
month = {Mon Oct 31 00:00:00 EST 2005}
}
  • The form of the grain size distribution strongly influences the linear dielectric response of a dusty plasma. For a class of size distributions and a thermal velocity distribution, there is an equivalence to a Lorentzian distribution of monosized particles. The electrostatic response to a slowly moving test charge can then be found. Dynamical charging of grains in a dusty plasma leads to an enhanced time-dependent shielding of a test charge. Here the combined effect of both grain size distribution and dynamical grain charging on the response to a slowly moving test charge is analyzed. The dynamical charging contribution to themore » plasma dielectric has a complicated dependence on the parameters for the size distribution and on the charging rate. However, this dependence can be expressed in terms of known functions. Series expansions are used to derive the potential response to a slowly moving test charge. Previously known results may be recovered as special limiting cases of this investigation. The analytical expression for the plasma dielectric may be used for more general cases and is applicable to the study of electrostatic waves.« less
  • The response potential of a dusty (complex) plasma to a moving test charge strongly depends on its velocity. For a test charge moving with a velocity exceeding the dust-acoustic speed, a distinctive wake-field is produced trailing behind the test charge. Here the response to a fast moving test charge, when dispersion effects are small and the dust behaves as a cold plasma component, is considered. The effects of dynamical grain charging are included, and the cases with and without these effects are analyzed and compared. The plasma dielectric function is chosen assuming that all grains are of the same sizemore » and includes a response term for charging dynamics. The wake field potential is found either explicitly in terms of known functions or by using numerical methods for the integral expression. Maximum response is found on the wake cone with apex angle determined by the ratio between the dust acoustic velocity and the test charge velocity. The structure of the wake field stretches in the direction of the test charge velocity when this increases. The functional form of the field is given by separately changing the length scales parallel and perpendicular to the velocity. The potential on the axis gives an electric field close behind the test charge that can attract charges with the same sign. The grain charging dynamics leads to a spatial damping and a phase shift in the potential response.« less
  • The effects of dust size distribution and charging process of dust grains on the complex electric conductivity of dusty plasmas have been investigated in the present paper. Comparisons are made between real dusty plasma in which there are many different dust grain species and the mono-sized dusty plasma (MDP) in which there is only one kind of dust grain whose size is the average dust size. In some cases the complex electric conductivity of real dusty plasma is larger than that of MDP, while in other cases it is smaller than that of MDP, it depends on the dust sizemore » distribution function.« less
  • The problem of grain screening is solved numerically for the case of weakly ionized plasma in the presence of an external magnetic field. The plasma dynamics is described within the drift-diffusion approximation under the assumption that the grain absorbs all encountered electrons and ions. We also assume that the plasma current through the grain surface is equal to zero in the stationary state. This condition is used to perform self-consistent calculations of the grain charge. The spatial distribution of the screened grain potential is studied and compared with the analytical estimates. It is shown that at the distances larger thanmore » the Debye length such potential has the Coulomb-like asymptotics with the effective charge dependent on the angle between the radius vector and the external magnetic field direction. The numerical solutions show that in the direction parallel to the external magnetic field the effective potential can have nonmonotonic behavior.« less
  • The Debye-Hueckel and oscillatory wake potentials caused by a test charge are studied in a multi-ion dusty plasma, whose constituents are the Boltzmann distributed electrons and light positive ions, the heavy mobile negative ions, and static but charge fluctuating dust particles. For this purpose, fluid equations are employed to obtain the dielectric constant of the dust-negative-ion acoustic wave involving the negative ions and dust charge fluctuation effects. Theoretical and numerical investigations have revealed the modification in the Debye-Hueckel and wake potentials due to the effects of dust relaxation rate, dust absorption frequency, dust grain radius, and negative ion temperature. Themore » present results should be important to form new materials in the presence of negative ions in laboratory as well as dust coagulation/agglomeration in space dusty plasmas.« less