Collisionless Plasma (collisionless + plasma)

Distribution by Scientific Domains


Selected Abstracts


Using the Steepened Plasma Profile and Wave Breaking Threshold in Laser-Plasma Interaction

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2008
P. Zobdeh
Abstract In this work we evaluate the interaction of high intense laser beam with a steepened density profile. During laser interaction with underdense plasma by freely expanding plasma regime, modification of density profile is possible. In this paper we have investigated the ultra short laser pulse interaction with nonisothermal and collisionless plasma. We consider self,focusing as an effective nonlinear phenomenon that tends to increase when the laser power is more than critical rate. By leading the expanded plasma to a preferred location near to critical density, laser reflection is obtained, so the density profile will be locally steepened. The electromagnetic fields are evaluated in this new profile. We show the amplitude and period of electrical field oscillation are increased by reducing the steepened scale length. Also our numerical results identify that by reducing the steepened scale length, the electrical field is increased to wave breaking threshold limit. This high gradient electrical field causes the effective beam loading during the wave breaking phenomenon. The wave breaking can be the initial point for other acceleration regime as cavity or channel guiding regime. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Sheath in Front of a Negatively Biased Collector that Emits Electrons and is Immersed in a Two Electron Temperature Plasma

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2005
T. Gyergyek
Abstract An extension of a recently published [Gyergyek T., ,er,ek M. Contrib. Plasma Phys., 45, (2005), 89] one dimensional fluid model of the sheath formation in front of a floating electrode (collector) that emits secondary electrons and is immersed in a two-electron temperature nonmagnetized, collisionless plasma is presented. The electron velocity distribution function is assumed to be a two-temperature maxwellian, while the singly charged positive ions and the emitted electrons are assumed to be monoenergetic. It is assumed that the electrons in the pre-sheath potential drop obey the Boltzmann relation, so that a larger fraction of the hot than of the cool electrons can penetrate to the sheath edge. Our model predicts that the collector can in some cases have 3 and in some cases, when the emission of electrons from the collector is critical, even 5 different floating potentials at the same hot to cool electron temperature and density ratios very far away from the collector. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Decay in time for a one-dimensional two-component plasma

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 18 2008
Robert Glassey
Abstract The motion of a collisionless plasma is described by the Vlasov,Poisson (VP) system, or in the presence of large velocities, the relativistic VP system. Both systems are considered in one space and one momentum dimension, with two species of oppositely charged particles. A new identity is derived for both systems and is used to study the behavior of solutions for large times. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Local existence for the one-dimensional Vlasov,Poisson system with infinite mass

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 5 2007
Stephen Pankavich
Abstract A collisionless plasma is modelled by the Vlasov,Poisson system in one dimension. We consider the situation in which mobile negative ions balance a fixed background of positive charge, which is independent of space and time, as ,x, , ,. Thus, the total positive charge and the total negative charge are both infinite. Smooth solutions with appropriate asymptotic behaviour are shown to exist locally in time, and criteria for the continuation of these solutions are established. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Counterstreaming magnetized plasmas with kappa distributions , I. Parallel wave propagation

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008
M. Lazar
ABSTRACT Non-thermal particle distributions of kappa type are frequently encountered in collisionless plasmas from space. The electromagnetic emissions coming from space are believed to originate in the counterstreaming structures of plasmas, which are ubiquitous in many astrophysical systems. Here, we investigate the dispersion properties and the stability of a counterstreaming plasma system with temperature anisotropies modelled by a bi-kappa distribution function. The numerical evaluation of parallel modes shows growth rates lower than those obtained for Maxwellian plasmas, with a strong dependence on the spectral index of the particle distribution function. If all other parameters are known, measuring the instability growth time can provide a possible tool for the determination of the spectral index ,. [source]


A possible origin of magnetic fields in galaxies and clusters: strong magnetic fields at z, 10?

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2005
Yutaka Fujita
ABSTRACT We propose that strong magnetic fields should be generated at shock waves associated with the formation of galaxies or clusters of galaxies by the Weibel instability, an instability in collisionless plasmas. The strength of the magnetic fields generated through this mechanism is close to the order of those observed in galaxies or clusters of galaxies at present. If the generated fields do not decay rapidly, this indicates that strong amplification of magnetic fields after the formation of galaxies or clusters of galaxies is not required. This mechanism could have worked even at a redshift of ,10, and therefore the generated magnetic fields may have affected the formation of stars in protogalaxies. This model will partially be confirmed by future observations of nearby clusters of galaxies. Mechanisms that preserve the magnetic fields for a long time without considerable decay are discussed. [source]