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| Titel |
The formation of relativistic plasma structures and their potential role in the generation of cosmic ray electrons |
| VerfasserIn |
M. E. Dieckmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 15, no. 6 ; Nr. 15, no. 6 (2008-11-03), S.831-846 |
| Datensatznummer |
250012801
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| Publikation (Nr.) |
 copernicus.org/npg-15-831-2008.pdf |
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| Zusammenfassung |
| Recent particle-in-cell (PIC) simulation studies have addressed particle
acceleration and magnetic field generation in relativistic astrophysical
flows by plasma phase space structures. We discuss the astrophysical
environments such as the jets of compact objects, and we give an overview
of the global PIC simulations of shocks. These reveal several types of
phase space structures, which are relevant for the energy dissipation.
These structures are typically coupled in shocks, but we choose to
consider them here in an isolated form. Three structures are reviewed.
(1) Simulations of interpenetrating or colliding plasma
clouds can trigger filamentation instabilities, while simulations of
thermally anisotropic plasmas observe the Weibel instability. Both
transform a spatially uniform plasma into current filaments. These
filament structures cause the growth of the magnetic fields. (2) The
development of a modified two-stream instability is discussed. It
saturates first by the formation of electron phase space holes. The
relativistic electron clouds modulate the ion beam and a secondary,
spatially localized electrostatic instability grows, which saturates by
forming a relativistic ion phase space hole. It accelerates electrons to
ultra-relativistic speeds. (3) A simulation is also revised, in which two
clouds of an electron-ion plasma collide at the speed 0.9c. The inequal
densities of both clouds and a magnetic field that is oblique to the
collision velocity vector result in waves with a mixed electrostatic
and electromagnetic polarity. The waves give rise to growing corkscrew
distributions in the electrons and ions that establish an equipartition
between the electron, the ion and the magnetic energy. The filament-,
phase space hole- and corkscrew structures are discussed with respect
to electron acceleration and magnetic field generation. |
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