12,257 research outputs found
Linear and nonlinear properties of Rao-dust-Alfv\'en waves in magnetized plasmas
The linear and nonlinear properties of the Rao-dust-magnetohydrodynamic
(R-D-MHD) waves in a dusty magnetoplasma are studied. By employing the
inertialess electron equation of motion, inertial ion equation of motion,
Amp\`ere's law, Faraday's law, and the continuity equation in a plasma with
immobile charged dust grains, the linear and nonlinear propagation of
two-dimensional R-D-MHD waves are investigated. In the linear regime, the
existence of immobile dust grains produces the Rao cutoff frequency, which is
proportional to the dust charge density and the ion gyrofrequency. On the other
hand, the dynamics of an amplitude modulated R-D-MHD waves is governed by the
cubic nonlinear Schroedinger equation. The latter has been derived by using the
reductive perturbation technique and the two-timescale analysis which accounts
for the harmonic generation nonlinearity in plasmas. The stability of the
modulated wave envelope against non-resonant perturbations is studied. Finally,
the possibility of localized envelope excitations is discussed.Comment: 30 pages, 8 figures, to appear in Physics of Plasma
Spinodal decomposition: An alternate mechanism of phase conversion
The scenario of homogeneous nucleation is investigated for a first order
quark-hadron phase transition in a rapidly expanding background of quark gluon
plasma. It is found that significant supercooling is possible before
hadronization begins. This study also suggests that spinodal decomposition
competes with nucleation and may provide an alternative mechanism for phase
conversion.Comment: LaTeX, 4 pages with 3 Postscript figures. Talk given at International
Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2001),
Nov. 26-30, 2001, Jaipur, Indi
Nonlinear wave-wave interactions in quantum plasmas
Wave-wave interaction in plasmas is a topic of important research since the
16th century. The formation of Langmuir solitons through the coupling of
high-frequency (hf) Langmuir and low-frequency (lf) ion-acoustic waves, is one
of the most interesting features in the context of turbulence in modern plasma
physics. Moreover, quantum plasmas, which are ubiquitous in ultrasmall
electronic devices, micromechanical systems as well as in dense astrophysical
environments are a topic of current research. In the light of notable interests
in such quantum plasmas, we present here a theoretical investigation on the
nonlinear interaction of quantum Langmuir waves (QLWs) and quantum ion-acoustic
waves (QIAWs), which are governed by the one-dimensional quantum Zakharov
equations (QZEs). It is shown that a transition to spatiotemporal chaos (STC)
occurs when the length scale of excitation of linear modes is larger than that
of the most unstable ones. Such length scale is, however, to be larger
(compared to the classical one) in presence of the quantum tunneling effect.
The latter induces strong QIAW emission leading to the occurrence of collision
and fusion among the patterns at an earlier time than the classical case.
Moreover, numerical simulation of the QZEs reveals that many solitary patterns
can be excited and saturated through the modulational instability (MI) of
unstable harmonic modes. In a longer time, these solitons are seen to appear in
the state of STC due to strong QIAW emission as well as by the collision and
fusion in stochastic motion. The energy in the system is thus strongly
redistributed, which may switch on the onset of Langmuir turbulence in quantum
plasmas.Comment: 6 pages, 6 figures (To appear in AIP Conf. Proceedings 2010
Nonlinear theory of solitary waves associated with longitudinal particle motion in lattices - Application to longitudinal grain oscillations in a dust crystal
The nonlinear aspects of longitudinal motion of interacting point masses in a
lattice are revisited, with emphasis on the paradigm of charged dust grains in
a dusty plasma (DP) crystal. Different types of localized excitations,
predicted by nonlinear wave theories, are reviewed and conditions for their
occurrence (and characteristics) in DP crystals are discussed. Making use of a
general formulation, allowing for an arbitrary (e.g. the Debye electrostatic or
else) analytic potential form and arbitrarily long site-to-site range
of interactions, it is shown that dust-crystals support nonlinear kink-shaped
localized excitations propagating at velocities above the characteristic DP
lattice sound speed . Both compressive and rarefactive kink-type
excitations are predicted, depending on the physical parameter values, which
represent pulse- (shock-)like coherent structures for the dust grain relative
displacement. Furthermore, the existence of breather-type localized
oscillations, envelope-modulated wavepackets and shocks is established. The
relation to previous results on atomic chains as well as to experimental
results on strongly-coupled dust layers in gas discharge plasmas is discussed.Comment: 21 pages, 12 figures, to appear in Eur. Phys. J.
Rossby rogons in atmosphere and in the solar photosphere
The generation of Rossby rogue waves (Rossby rogons), as well as the
excitation of bright and dark Rossby envelpe solitons are demonstrated on the
basis of the modulational instability (MI) of a coherent Rossby wave packet.
The evolution of an amplitude modulated Rossby wave packet is governed by
one-dimensional (1D) nonlinear Schr\"odinger equation (NLSE). The latter is
used to study the amplitude modulation of Rossby wave packets for fluids in
Earth's atmosphere and in the solar photosphere. It is found that an ampitude
modulated Rossby wave packet becomes stable (unstable) against
quasi-stationary, long wavelength (in comparision with the Rossby wave length)
perturbations, when the carrier Rossby wave number satisfies or
or ). It is also shown that a
Rossby rogon or a bright Rossby envelope soliton may be excited in the shallow
water approximation for the Rossby waves in solar photosphere. However, the
excitation of small or large scale perturbations may be possible for magnetized
plasmas in the ionosphereic layer.Comment: 6 pages, 5 figures; To appear in Europhysics Letter
Self-Diffusion in 2D Dusty Plasma Liquids: Numerical Simulation Results
We perform Brownian dynamics simulations for studying the self-diffusion in
two-dimensional (2D) dusty plasma liquids, in terms of both mean-square
displacement and velocity autocorrelation function (VAF). Super-diffusion of
charged dust particles has been observed to be most significant at infinitely
small damping rate for intermediate coupling strength, where the
long-time asymptotic behavior of VAF is found to be the product of and
. The former represents the prediction of early theories in
2D simple liquids and the latter the VAF of a free Brownian particle. This
leads to a smooth transition from super-diffusion to normal diffusion, and then
to sub-diffusion with an increase of the damping rate. These results well
explain the seemingly contradictory scattered in recent classical molecular
dynamics simulations and experiments of dusty plasmas.Comment: 10 pages 5 figures, accepted by PR
Dust acoustic wave in a strongly magnetized pair-dust plasma
The existence of the dust acoustic wave (DAW) in a strongly magnetized
electron-positron (pair)-dust plasma is demonstrated. In the DAW, the restoring
force comes from the pressure of inertialess electrons and positrons, and the
dust mass provides the inertia. The waves could be of interest in astrophysical
settings such as the supernovae and pulsars, as well as in cluster explosions
by intense laser beams in laboratory plasmas.Comment: 6 pages, revtex
Modulational instability in asymmetric coupled wave functions
The evolution of the amplitude of two nonlinearly interacting waves is
considered, via a set of coupled nonlinear Schroedinger-type equations. The
dynamical profile is determined by the wave dispersion laws (i.e. the group
velocities and the GVD terms) and the nonlinearity and coupling coefficients,
on which no assumption is made. A generalized dispersion relation is obtained,
relating the frequency and wave-number of a small perturbation around a coupled
monochromatic (Stokes') wave solution. Explicitly stability criteria are
obtained. The analysis reveals a number of possibilities. Two (individually)
stable systems may be destabilized due to coupling. Unstable systems may, when
coupled, present an enhanced instability growth rate, for an extended wave
number range of values. Distinct unstable wavenumber windows may arise
simultaneously.Comment: NEXT Sigma-Phi Statistical Physics Conference (2005, Kolymbari,
Greece) Proceedings, submitted; v.2 is a shorter version of the text in v.1
(more detailed and somehow more explanatory, yet abbreviated due to
submission regulations); some typos corrected as wel
Nonlinear modulation of transverse dust lattice waves in complex plasma crystals
The occurrence of the modulational instability (MI) in transverse dust
lattice waves propagating in a one-dimensional dusty plasma crystal is
investigated. The amplitude modulation mechanism, which is related to the
intrinsic nonlinearity of the sheath electric field, is shown to destabilize
the carrier wave under certain conditions, possibly leading to the formation of
localized envelope excitations. Explicit expressions for the instability growth
rate and threshold are presented and discussed.Comment: 5 pages, no figures; submitted to Physics of Plasma
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