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Dusty plasma response to a moivng test charge
KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
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. , p. xii, 50
Series
Trita-ALP, ISSN 1103-6613 ; 2005:03
Keywords [en]
Physics, Dusty Plasmas, Complex Plasmas, Grain size distribution, Grain charging dynamics
Keywords [sv]
Fysik
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-298ISBN: 91-7178-040-8 (print)OAI: oai:DiVA.org:kth-298DiVA, id: diva2:8722
Presentation
2005-05-24, 11:00
Supervisors
Note
QC 20101220Available from: 2005-07-11 Created: 2005-07-11 Last updated: 2011-10-28Bibliographically approved
List of papers
1. Test charge response of a dusty plasma with a grain size distribution
Open this publication in new window or tab >>Test charge response of a dusty plasma with a grain size distribution
2002 (English)In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 305, p. 79-86Article 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 there is an equivalence to a Lorentzian distribution of mono-sized particles. The electrostatic response to a slowly moving test charge, using a second order approximation, is found. The effects of collisions are investigated.

Keywords
dusty plasmas, complex plasmas, grain size distribution, Lorentzian distribution, Kappa distribution, test charge response
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-6230 (URN)10.1016/S0375-9601(02)01392-0 (DOI)000179601000012 ()
Note
QC 20100917Available from: 2006-10-06 Created: 2006-10-06 Last updated: 2017-12-14Bibliographically approved
2. Shielding of a slowly moving test charge in a dusty plasma with dynamical grain charging
Open this publication in new window or tab >>Shielding of a slowly moving test charge in a dusty plasma with dynamical grain charging
2003 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 10, no 9, p. 3484-3491Article 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.

Keywords
energy-loss, acoustic-wave, halleys-comet, projectiles, particles
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-6231 (URN)10.1063/1.1598433 (DOI)000184899800007 ()
Note
QC 20100917Available from: 2006-10-06 Created: 2006-10-06 Last updated: 2017-12-14Bibliographically approved
3. Delayed shielding of a test charge due to dynamical grain charging in a dusty plasma
Open this publication in new window or tab >>Delayed shielding of a test charge due to dynamical grain charging in a dusty plasma
2004 (English)In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 32, p. 627-631Article in journal (Refereed) Published
Abstract [en]

The dynamical charging of grains in a dusty plasma modifies the plasma dielectric response function and the nature of the electrostatic wave modes. The grain charging leads to an additional shielding effect that acts in the same way as Debye shielding. Both the additional shielding and the charging rate are important in determining the response of a dusty plasma to a moving test charge. The dynamics of the charging can be approximated by using a time delay. An alternative analysis of the potential of a slowly moving test charge is performed introducing a delay operator for the grain charge response. 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 gives a physical interpretation of earlier results which are identical to first order in the test charge velocity.

Keywords
Complex plasmas, dusty plasmas, dynamical grain charging, test charge response
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-6232 (URN)10.1109/TPS.2004.828451 (DOI)000222278400018 ()2-s2.0-4344715426 (Scopus ID)
Note
QC 20100920. Title changed from "Delayed shielding of a slowly moving test charge in a dusty plasma with dynamical grain charging".Available from: 2006-10-06 Created: 2006-10-06 Last updated: 2017-12-14Bibliographically approved

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