3,616 research outputs found
Ferromagnetic behavior in magnetized plasmas
We consider a low-temperature plasma within a newly developed MHD Fluid
model. In addition to the standard terms, the electron spin, quantum particle
dispersion and degeneracy effects are included. It turns out that the electron
spin properties can give rise to Ferromagnetic behavior in certain regimes. If
additional conditions are fulfilled, a homogenous magnetized plasma can even be
unstable. This happen in the low-temperature high-density regime, when the
magnetic properties associated with the spin can overcome the stabilizing
effects of the thermal and Fermi pressure, to cause a Jeans like instability.Comment: 4 pages, 1 figur
Semiclassical Vlasov and fluid models for an electron gas with spin effects
We derive a four-component Vlasov equation for a system composed of spin-1/2
fermions (typically electrons). The orbital part of the motion is classical,
whereas the spin degrees of freedom are treated in a completely
quantum-mechanical way. The corresponding hydrodynamic equations are derived by
taking velocity moments of the phase-space distribution function. This
hydrodynamic model is closed using a maximum entropy principle in the case of
three or four constraints on the fluid moments, both for Maxwell-Boltzmann and
Fermi-Dirac statistics.Comment: To appear in the European Physical Journal D, Topical Issue "Theory
and Applications of the Vlasov Equation
Phase-space structures in quantum-plasma wave turbulence
The quasilinear theory of the Wigner-Poisson system in one spatial dimension
is examined. Conservation laws and properties of the stationary solutions are
determined. Quantum effects are shown to manifest themselves in transient
periodic oscillations of the averaged Wigner function in velocity space. The
quantum quasilinear theory is checked against numerical simulations of the
bump-on-tail and the two-stream instabilities. The predicted wavelength of the
oscillations in velocity space agrees well with the numerical results
Modified Zakharov equations for plasmas with a quantum correction
Quantum Zakharov equations are obtained to describe the nonlinear interaction
between quantum Langmuir waves and quantum ion-acoustic waves. These quantum
Zakharov equations are applied to two model cases, namely the four-wave
interaction and the decay instability. In the case of the four-wave
instability, sufficiently large quantum effects tend to suppress the
instability. For the decay instability, the quantum Zakharov equations lead to
results similar to those of the classical decay instability except for quantum
correction terms in the dispersion relations. Some considerations regarding the
nonlinear aspects of the quantum Zakharov equations are also offered.Comment: 4 figures. Accepted for publication in Physics of Plasmas (2004
Bound states near a moving charge in a quantum plasma
It is investigated how the shielding of a moving point charge in a
one-component fully degenerate fermion plasma affects the bound states near the
charge at velocities smaller than the Fermi one. The shielding is accounted for
by using the Lindhard dielectric function, and the resulting potential is
substituted into the Schr\"odinger equation in order to obtain the energy
levels. Their number and values are shown to be primarily determined by the
value of the charge and the quantum plasma coupling parameter, while the main
effect of the motion is to split certain energy levels. This provides a link
between quantum plasma theory and possible measurements of spectra of ions
passing through solids.Comment: Published in EPL, see
http://epljournal.edpsciences.org/articles/epl/abs/2011/09/epl13478/epl13478.htm
Connection between the two branches of the quantum two-stream instability across the k space
The stability of two quantum counter-streaming electron beams is investigated
within the quantum plasma fluid equations for arbitrarily oriented wave
vectors. The analysis reveals that the two quantum two-stream unstable branches
are indeed connected by a continuum of unstable modes with oblique wave
vectors. Using the longitudinal approximation, the stability domain for any k
is analytically explained, together with the growth rate
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