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Test charge response for a dusty plasma with both grain size distribution and dynamical charging
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
2007 (English)In: Physics of Plasmas, ISSN 1070-664X, Vol. 14, no 1, 012105- p.Article in journal (Refereed) Published
Abstract [en]

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 the 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.

Place, publisher, year, edition, pages
2007. Vol. 14, no 1, 012105- p.
Keyword [en]
moving test charge, energy-loss, dispersion function, projectiles, particles
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-6234DOI: 10.1063/1.2431354ISI: 000243891800010Scopus ID: 2-s2.0-34047117705OAI: oai:DiVA.org:kth-6234DiVA: diva2:10884
Note
Uppdaterad från "in press" till published. QC 20100920Available from: 2006-10-06 Created: 2006-10-06 Last updated: 2010-09-20Bibliographically approved
In thesis
1. Test Charge Response of a Dusty Plasma with Grain Size Distribution and Charging Dynamics
Open this publication in new window or tab >>Test Charge Response of a Dusty Plasma with Grain Size Distribution and Charging Dynamics
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This doctoral thesis reports analytical and numerical results for the electrostatic response of a dusty plasma to a moving test charge. Two important physical aspects of dusty plasmas, namely grain size distribution and grain charging dynamics were taken into account. In the first case, a dusty plasma in thermal equilibrium and with a distribution of grain sizes is considered. A size distribution is assumed which decreases exponentially with the grain mass for large sizes and gives a simple smooth reduction for small sizes. The electrostatic response to a slowly moving test charge, using a second order approximation is found and the effects of collisions are also investigated. It turns out that for this particular size distribution, there is a remarkably simple result that the resulting effective distribution for the electrostatic response is a kappa (generalized Lorentzian) distribution. In the second case, we present an analytical model for the shielding of a slowly moving test charge in a dusty plasma with dynamical grain charging for cases both with and without the collision effects. The response potential is treated as a power series in test charge velocity. Analytical expressions for the response potential are found up to second order in test charge velocity. The first-order dynamical charging term is shown to be the consequence of the delay in the shielding due to the dynamics of the charging process. It is concluded that the dynamical charging of the grains in a dusty plasma enhances the shielding of a test charge. To clarify the physics, a separate study is made where the charging is approximated by using a time delay. The resulting potential shows the delayed shielding effect explicitly. The terms in the potential that depend on the charging dynamics involve a spatial shift given by the test charge velocity and the charging time. The wake potential of a fast moving test charge in the case of grain charging dynamics was also found. It was observed that the grain charging dynamics leads to a spatial damping and a phase shift in the potential response. Finally, combining these two physical aspects, generalized results for the electrostatic potential were found incorporating the terms from both grain size distribution and grain charging dynamics. The generalized results contain the previous work where these two effects were studied separately and which can now be found as special limiting cases. This kind of work has relevance both in space and astrophysical plasmas.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xviii, 65 p.
Series
Trita-EE, ISSN 1653-5146 ; 2006:045
Keyword
Dusty plasmas, Complex plasmas, Grain size distribution, Grain charging dynamics, Lorentzian distribution, Kappa distribution, Test charge response, Delayed shielding, Energy loss, Drag force, Wake field.
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-4134 (URN)91-7178-463-2 (ISBN)
Public defence
2006-10-31, KTHB Salongen, Main Library, Osquars Backe 31, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100920Available from: 2006-10-06 Created: 2006-10-06 Last updated: 2011-10-28Bibliographically approved

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