The plasma filamentation instability in one dimension: nonlinear evolution
Rowlands, G. (George), Dieckmann, M. E. and Shukla, P. K.. (2007) The plasma filamentation instability in one dimension: nonlinear evolution. New Journal of Physics, Vol.9 . Article: 247. ISSN 1367-2630Full text not available from this repository.
Official URL: http://dx.doi.org/10.1088/1367-2630/9/8/247
The plasma filamentation instability or beam-Weibel instability generates magnetic fields and accelerates particles in collisionless astrophysical plasma. This instability has been examined with multi-dimensional particle-incell (PIC) simulations, demonstrating the formation of current flux tubes. Such simulations could not model a statistically significant number of filaments. Here, we model with a PIC simulation the filamentation instability that is driven by nonrelativistic, cool electron beams in one spatial dimension at an unprecedented resolution. We show unambiguously that the gradient of the magnetic pressure which develops during the quasi-linear evolution of the filamentation instability, gives rise to an electrostatic field component. The interplay of the magnetic and electrostatic fields results in a wavenumber spectrum of the magnetic field that is a power-law, which has been reported previously for multi-dimensional PIC simulations. The magnetic field power spectrum decreases with the exponent -5.7 and that of the electrostatic field with -3.8, yielding a ratio of 3:2. The electromagnetic fields thermalize the electrons. The electrons develop a velocity distribution in the simulation direction that decreases exponentially at low speeds and faster at high speeds. The filamentation instability can thus not efficiently accelerate electrons to high energies. The filaments develop into a stationary final state. The probability distribution of the filament sizes is a Gumbel distribution. In astrophysical settings, this implies that the long exponential tail of this distribution may lead with a reasonable probability to large current filaments, if the filamentation instability develops in a large enough volume. The coherent magnetic fields of large filaments are required to explain the synchrotron emissions of gamma ray bursts.
|Item Type:||Journal Article|
|Subjects:||Q Science > QC Physics|
|Divisions:||Faculty of Science > Physics|
|Journal or Publication Title:||New Journal of Physics|
|Official Date:||1 August 2007|
|Number of Pages:||16|
|Page Range:||Article: 247|
|Access rights to Published version:||Open Access|
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