154 research outputs found
Large-amplitude electron-acoustic solitons in a dusty plasma with kappa-distributed electrons
The Sagdeev pseudopotential method is used to investigate the occurrence and
the dynamics of fully nonlinear electrostatic solitary structures in a plasma
containing suprathermal hot electrons, in the presence of massive charged dust
particles in the background. The soliton existence domain is delineated, and
its parametric dependence on different physical parameters is clarified.Comment: 3 pages, 1 figure, presented as a poster at the 6th International
Conference on the Physics of Dusty Plasmas (ICPDP6), Garmisch-Partenkirchen,
Germany, 201
Oblique amplitude modulation of dust-acoustic plasma waves
Theoretical and numerical studies are presented of the nonlinear amplitude
modulation of dust-acoustic (DA) waves propagating in an unmagnetized three
component, weakly-coupled, fully ionized plasma consisting of electrons,
positive ions and charged dust particles, considering perturbations oblique to
the carrier wave propagation direction. The stability analysis, based on a
nonlinear Schroedinger-type equation (NLSE), shows that the wave may become
unstable; the stability criteria depend on the angle between the
modulation and propagation directions. Explicit expressions for the instability
rate and threshold have been obtained in terms of the dispersion laws of the
system. The possibility and conditions for the existence of different types of
localized excitations have also been discussed.Comment: 21 pages, 6 figures, to appear in Physica Script
Random walk of magnetic field lines for different values of the energy-range spectral index
An analytical nonlinear description of field-line wandering in partially
statistically magnetic systems was proposed recently [A. Shalchi, I. Kourakis,
Astronomy and Astrophysics, 470, 405 (2007)]. In this article we investigate
the influence of the wave-spectrum in the energy-range onto field line random
walk by applying this formulation. It is demonstrated that in all considered
cases we clearly obtain a superdiffusive behaviour of the field-lines. If the
energy-range spectral index exceeds unity a free-streaming behaviour of the
field-lines can be found for all relevant length-scales of turbulence. Since
the superdiffusive results obtained for the slab model are exact, it seems that
superdiffusion is the normal behavior of field line wandering.Comment: Submitted to Physics of Plasmas; 13 pages, no figure
Discrete Breathers in Hexagonal Dusty Plasma Lattices
The occurrence of single- or multisite localized vibrational modes, also
called Discrete Breathers (DBs), in 2D hexagonal dusty plasma (DP) lattices is
investigated. The system is described by a Klein-Gordon hexagonal lattice
characterized by a negative coupling parameter \e in account of its inverse
dispersive behavior. A theoretical analysis is performed in order to establish
the possibility of existence of single- as well as three-site DBs in such
systems. The study is complemented by a numerical investigation based on
experimentally provided potential forms. This investigation shows that a DP
lattice can support single site DBs while three-site in phase breathers could
exist if specific conditions, about the inter-grain interaction strength, would
hold. On the other hand, out of phase and vortex three site breathers cannot be
supported since they are highly unstable
Oblique propagation of arbitrary amplitude electron acoustic solitary waves in magnetized kappa-distributed plasmas
The linear and nonlinear properties of large amplitude electron-acoustic
waves are investigated in a magnetized plasma comprising two distinct electron
populations (hot and cold) and immobile ions. The hot electrons are assumed to
be in a non-Maxwellian state, characterized by an excess of superthermal
particles, here modelled by a kappa-type long-tailed distribution function.
Waves are assumed to propagate obliquely to the ambient magnetic field. Two
types of electrostatic modes are shown to exist in the linear regime, and their
properties are briefly analyzed. A nonlinear pseudopotential type analysis
reveals the existence of large amplitude electrostatic solitary waves and
allows for an investigation of their propagation characteristics and existence
domain, in terms of the soliton speed (Mach number). The effects of the key
plasma configuration parameters, namely, the superthermality index and the cold
electron density, on the soliton characteristics and existence domain, are
studied. The role of obliqueness and magnetic field are discussed.Comment: Submitted to Plasma Physics and Controlled Fusio
Discrete solitons and vortices in hexagonal and honeycomb lattices: Existence, stability, and dynamics
We consider a prototypical dynamical lattice model, namely, the discrete
nonlinear Schroedinger equation on nonsquare lattice geometries. We present a
systematic classification of the solutions that arise in principal
six-lattice-site and three-lattice-site contours in the form of both discrete
multipole solitons and discrete vortices. Additionally to identifying the
possible states, we analytically track their linear stability both
qualitatively and quantitatively. We find that among the six-site
configurations, the hexapole of alternating phases, as well as the vortex of
topological charge S=2 have intervals of stability; among three-site states,
only the vortex of topological charge S=1 may be stable in the case of focusing
nonlinearity. These conclusions are confirmed both for hexagonal and for
honeycomb lattices by means of detailed numerical bifurcation analysis of the
stationary states from the anticontinuum limit, and by direct simulations to
monitor the dynamical instabilities, when the latter arise. The dynamics reveal
a wealth of nonlinear behavior resulting not only in single-site solitary wave
forms, but also in robust multisite breathing structures
Nonlinear magnetoinductive transmission lines
Power transmission in one-dimensional nonlinear magnetic metamaterials driven
at one end is investigated numerically and analytically in a wide frequency
range. The nonlinear magnetic metamaterials are composed of varactor-loaded
split-ring resonators which are coupled magnetically through their mutual
inductances, forming thus a magnetoiductive transmission line. In the linear
limit, significant power transmission along the array only appears for
frequencies inside the linear magnetoinductive wave band. We present
analytical, closed form solutions for the magnetoinductive waves transmitting
the power in this regime, and their discrete frequency dispersion. When
nonlinearity is important, more frequency bands with significant power
transmission along the array may appear. In the equivalent circuit picture, the
nonlinear magnetoiductive transmission line driven at one end by a relatively
weak electromotive force, can be modeled by coupled
resistive-inductive-capacitive (RLC) circuits with voltage-dependent
capacitance. Extended numerical simulations reveal that power transmission
along the array is also possible in other than the linear frequency bands,
which are located close to the nonlinear resonances of a single nonlinear RLC
circuit. Moreover, the effectiveness of power transmission for driving
frequencies in the nonlinear bands is comparable to that in the linear band.
Power transmission in the nonlinear bands occurs through the linear modes of
the system, and it is closely related to the instability of a mode that is
localized at the driven site.Comment: 11 pages, 11 figures, submitted to International Journal of
Bifurcation and Chao
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