1,132 research outputs found
A linearized kinetic theory of spin-1/2 particles in magnetized plasmas
We have considered linear kinetic theory including the electron spin
properties in a magnetized plasma. The starting point is a mean field
Vlasov-like equation, derived from a fully quantum mechanical treatment, where
effects from the electron spin precession and the magnetic dipole force is
taken into account. The general conductivity tensor is derived, including both
the free current contribution, as well as the magnetization current associated
with the spin contribution. We conclude the paper with an extensive discussion
of the quantum-mechanical boundary where we list parameter conditions that must
be satisfied for various quantum effects to be influential.Comment: 11 page
Spin quantum plasmas - new aspects of collective dynamics
Quantum plasmas is a rapidly expanding field of research, with applications
ranging from nanoelectronics, nanoscale devices and ultracold plasmas, to
inertial confinement fusion and astrophysics. Here we give a short systematic
overview of quantum plasmas. In particular, we analyze the collective effects
due to spin using fluid models. The introduction of an intrinsic magnetization
due to the plasma electron (or positron) spin properties in the
magnetohydrodynamic limit is discussed. Finally, a discussion of the theory and
examples of applications is given.Comment: 17 pages, short review concerning quantum plasmas, to appear in the
Proceedings of the 2007 ICTP Summer College on Plasma Physics, Trieste 30
July - 24 August, 200
Exact analytic solutions for nonlinear waves in cold plasmas
Large amplitude plasma oscillations are studied in a cold electron plasma. Using Lagrangian variables, a new class of exact analytical solutions is found. It turns out that the electric field amplitude is limited either by wave breaking or by the condition that the electron density always has to stay positive. The range of possible amplitudes is determined analytically
Particle-in-Cell simulations of electron spin effects in plasmas
We have here developed a particle-in-cell code accounting for the magnetic
dipole force and for the magnetization currents associated with the electron
spin. The electrons is divided into spin-up and spin-down populations relative
to the magnetic field, where the magnetic dipole force acts in opposite
directions for the two species. To validate the code, we have studied the
wakefield generation by an electromagnetic pulse propagating parallel to an
external magnetic field. The properties of the generated wakefield is shown to
be in good quantitative agreement with previous theoretical results.
Generalizations of the code to account for more quantum effects is discussedComment: 5 pages, 6 figure
On the contribution of exchange interactions to the Vlasov equation
Exchange effects play an important role in determining the equilibrium
properties of dense matter systems, as well as for magnetic phenomena. There
exists an extensive literature concerning, e.g., the effects of exchange
interactions on the equation of state of dense matter. Here, a generalization
of the Vlasov equation to include exchange effects is presented allowing for
electromagnetic mean fields, thus incorporating some of the dynamic effects due
to the exchange interactions. Treating the exchange term perturbatively, the
correction to classical Langmuir waves in plasmas is found, and the results are
compared with previous work. It is noted that the relative importance of
exchange effects scales similarly with density and temperature as particle
dispersive effects, but that the overall magnitude is sensitive to the details
of the specific problem. The implications of our results are discussed.Comment: 9 page
Spin induced nonlinearities in the electron MHD regime
We consider the influence of the electron spin on the nonlinear propagation
of whistler waves. For this purpose a recently developed electron two-fluid
model, where the spin up- and down populations are treated as different fluids,
is adapted to the electron MHD regime. We then derive a nonlinear Schrodinger
equation for whistler waves, and compare the coefficients of nonlinearity with
and without spin effects. The relative importance of spin effects depend on the
plasma density and temperature as well as the external magnetic field strength
and the wave frequency. The significance of our results to various plasmas are
discussed.Comment: 5 page
Nonlinear coupled Alfv\'{e}n and gravitational waves
In this paper we consider nonlinear interaction between gravitational and
electromagnetic waves in a strongly magnetized plasma. More specifically, we
investigate the propagation of gravitational waves with the direction of
propagation perpendicular to a background magnetic field, and the coupling to
compressional Alfv\'{e}n waves. The gravitational waves are considered in the
high frequency limit and the plasma is modelled by a multifluid description. We
make a self-consistent, weakly nonlinear analysis of the Einstein-Maxwell
system and derive a wave equation for the coupled gravitational and
electromagnetic wave modes. A WKB-approximation is then applied and as a result
we obtain the nonlinear Schr\"{o}dinger equation for the slowly varying wave
amplitudes. The analysis is extended to 3D wave pulses, and we discuss the
applications to radiation generated from pulsar binary mergers. It turns out
that the electromagnetic radiation from a binary merger should experience a
focusing effect, that in principle could be detected.Comment: 20 pages, revtex4, accepted in PR
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