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Phase space vortices in collision-less plasmas
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Division of Astronomy and Space Physics.
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2003 (English)In: Nonlinear processes in geophysics, ISSN 1023-5809, Vol. 10, no 1/2, 75-86 p.Article in journal (Refereed) Published
Abstract [en]

Results on the formation and propagation of electron phase space vortices from laboratory experiments are summarized. The electron phase space vortices were excited in a strongly magnetized Q-machine plasma by applying a pulse to a segment of a waveguide surrounding the plasma. Depending on the temporal variation of the applied pulse, one or more phase space vortices can be excited, and their interaction can be followed in space and time. We were able to demonstrate, for instance, an irreversible coalescence of two such vortices. These results are extended by numerical simulations, showing how electron phase space vortices can also be formed by beam instabilities. Furthermore, a study of ion phase space vortices is performed by numerical simulations. Both codes allow for an externally applied magnetic field in three spatial dimensions. Ion phase space vortices are formed by the nonlinear saturation of the ion-ion two-stream instability, excited by injecting an ion beam at the plasma boundary. By following the evolution of the ion distribution of the velocity perpendicular to the direction of propagation of the injected ion beam, we find a significant ion heating in the direction perpendicular to the magnetic field associated with the ion phase space vortices being formed. The results are relevant, for instance, for the interpretation of observations by instrumented spacecraft in the Earth's ionosphere and magnetosphere.

Place, publisher, year, edition, pages
2003. Vol. 10, no 1/2, 75-86 p.
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-97954OAI: oai:DiVA.org:uu-97954DiVA: diva2:173084
Available from: 2009-01-01 Created: 2009-01-01 Last updated: 2009-09-24Bibliographically approved
In thesis
1. Numerical Simulation as a Tool for Studying Waves and Radiation in Space
Open this publication in new window or tab >>Numerical Simulation as a Tool for Studying Waves and Radiation in Space
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Plasma physics governs the area of interactions between charged particles. As 99% of the visible universe is in a plasma state, it is an important topic in astronomy and space physics, where we already at an altitude of 60 km reach the plasma environment surrounding our planet in the form of the ionosphere. The search for fusion, the source of power for the sun, as well as industrial use have been the main topics for earth bound plasma reasurch.

A plasma is composed of charged particles which interact by the electromagnetic force. In the kinetic description, via the Vlasov-Maxwell equations, the system is described in terms of probability distribution functions for each particle species, expressed in terms of particles position and velocity. The particles interact via self-consistent fields as determined by Maxwell's equations. For understanding the complex behaviour of the system, we need numerical solvers. These come in two flavours, Lagrangian methods, dealing with the moving around of synthetic particles, and Eulerian methods, which solve the set of partial differential, Vlasov and Maxwell equations. To perform the computations within reasonable time, we need to distribute our calculations on multiple machines, i.e. parallel programming, with the best possible matching between our computational needs and the need of splitting algorithms to adapt to our processing environment.

Paper I studies electron and ion beams within a Lagrangian and fluid model and compare the results with experimental observations. This is continued with studies of a full kinetic system, using an Eulerian solver, for a closer look at electron-ion interactions in relation to ionospheric observations, (Papers II and IV). To improve the performance of the Eulerian solver it was parallelised (Paper III). The thesis is ending with the possibility to observe ultrahigh energy neutrinos from an orbiting satellite by using the Moon's surface as a detector Paper V.

Place, publisher, year, edition, pages
Uppsala: Universitetsbiblioteket, 2008. 42 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 488
space physics, plasma physics, kinetic plasma, plasma simulations, beam instabilities
National Category
Fusion, Plasma and Space Physics
urn:nbn:se:uu:diva-9517 (URN)978-91-554-7384-6 (ISBN)
Public defence
2009-01-30, Siegbhansalen, Ångström Laboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Available from: 2009-01-01 Created: 2009-01-01 Last updated: 2010-03-09Bibliographically approved

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