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Shielding of a slowly moving test charge in a dusty plasma with dynamical grain charging
KTH, Superseded Departments, Alfvén Laboratory.
KTH, Superseded Departments, Alfvén Laboratory.
2003 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 10, no 9, 3484-3491 p.Article in journal (Refereed) Published
Abstract [en]

The dynamical charging of grains in a dusty plasma enhances the shielding of test charges. Time scales for charging are determined by the ambient plasma parameters and the grain dimensions. They can be very short, approaching the ion plasma period for grain sizes of the order of an electron Debye length. For a slowly moving test charge the response potential is found as a power series in the test charge velocity. Collisional effects are included. Analytical expressions for the response potential, valid for all radial distances, are found up to second order in the 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. The remaining first-order terms are given by analytical expressions that yield the well known asymptotic power law forms for large distances.

Place, publisher, year, edition, pages
2003. Vol. 10, no 9, 3484-3491 p.
Keyword [en]
energy-loss, acoustic-wave, halleys-comet, projectiles, particles
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-6231DOI: 10.1063/1.1598433ISI: 000184899800007OAI: oai:DiVA.org:kth-6231DiVA: diva2:10881
Note
QC 20100917Available from: 2006-10-06 Created: 2006-10-06 Last updated: 2017-12-14Bibliographically 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
2. Dusty plasma response to a moivng test charge
Open this publication in new window or tab >>Dusty plasma response to a moivng test charge
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This licentiate thesis reports analytical results for the electrostatic response to a test charge moving through dusty plasma. Two particular cases for a slowly moving test charge, namely, grain size distribution and grain charging dynamics are considered. Analytical results for the delayed shielding of a test charge due to dynamical grain charging in dusty plasma are also reported. 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. This kind of work has relevance both in space and astrophysical plasmas.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xii, 50 p.
Series
Trita-ALP, ISSN 1103-6613 ; 2005:03
Keyword
Physics, Dusty Plasmas, Complex Plasmas, Grain size distribution, Grain charging dynamics, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-298 (URN)91-7178-040-8 (ISBN)
Presentation
2005-05-24, 11:00
Supervisors
Note
QC 20101220Available from: 2005-07-11 Created: 2005-07-11 Last updated: 2011-10-28Bibliographically approved

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