Abstract: Kelley's solution for the incompressible viscous flow past an infinite wall, with time dependent suction, is extended for an idealized elastico-viscous liquid. The effect of the presence of the elasticity on the velocity field and the skin friction is examined. It is found that the back-flow at the wall is enhanced by the elasticity parameter. The phase angle of the skin friction is also found to decrease with increasing the unsteady part or the suction velocity.
Abstract: It is shown that Grad hydrodynamics dan be used for the description of nonlinear ion-drift waves in a low beta plasma. The set of nonlinear equations which allows us to describe both the ion polarization drift and the nonzero ion Larmor;radius effects is derived. The presence of a nonzero ion temperature gradient induces a corresponding perpendicular thermal flux which in turn substantially modifies; the transverse stress tensor. Thus, the description of effects associated with the perpendicular ion polarization drift demands corrections in the magnetic viscosity due to the nonzero thermal flux. (C) 2001 American Institute of Physics. [DOI: 10.1063/1.1316764].
Abstract: We derive a system of nonlinear equations governing the dynamics of low-frequency electrostatic waves in a magnetized pair plasma with sheared flows that is contaminated by dust grains. For some specific profiles of the equilibrium sheared flows, the nonlinear equations admit a stationary solution in the form of a tripolar vortex. The implications of our investigation to laboratory and space plasmas are discussed.
Abstract: Cylindrical wave diffraction by a slit in an infinite, plane, perfectly conducting barrier in a homogeneous biisotropic medium is investigated. The source point is assumed far from the slit so that the incident cylindrical wave is locally plane. The slit is wide and the barrier thin, both with respect to wavelength. The boundary value problem is reduced to a Wiener-Hopf equation and solved approximately.
Abstract: By employing a two fluid model, a set of equations for ion pressure gradient driven low-frequency (in comparison with the ion-gyrofrequency) electrostatic waves in a collisional magnetoplasma has been derived. The equations exhibit a coupling between the electrostatic potential, the parallel ion velocity and ion-temperature perturbations. In the linear limit, a new dispersion relation has been derived and analyzed numerically to demonstrate the existence of ion-temperature-gradient driven drift-dissipative modes. Since in a highly collisional plasma there is a departure from the Boltzmann electron response, there appears anomalous particle and ion-energy transports due to nonthermal fluctuations. Taking some typical tokamak parameters, the transport coefficients are numerically depicted for maximally growing drift wave fluctuations. The results of our investigation are useful for the understanding of fluctuation driven transports in tokamak edges in which collisions are dominant.
Abstract: A system of nonlinear equations for low-frequency toroidal ion-temperature-gradient modes in a nonuniform magnetoplasma with sheared plasma flow is presented. For some specific profiles of the equilibrium density, the ion temperature and sheared plasma flows, the nonlinear equations admit a tripolar vortex. The numerical results show a negative potential vortex core between the lobs of a dipole-like structure which has a positive value of the potential. (C) 2001 American Institute of Physics.
Abstract: It is shown that the nonlinear equation governing the dynamics of coupled dust-acoustic and dust-cyclotron waves in a magnetized dust-ion plasma can be written in the form of an energy integral. The latter is analyzed analytically as well as numerically to investigate the properties of arbitrary amplitude solitary waves. It is found both analytically as well as numerically that there exist solitary waves only with a negative potential. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring systems and cometary tails, are briefly discussed. (C) 2001 American Institute of Physics.
Abstract: Nonlinear equations governing the dynamics of finite amplitude drift-acoustic-waves are derived, taking into account sheared ion flows. A new class of stationary solution of the nonlinear equations can be represented in the form of a counter-rotating vortex. The latter appears in those parameter regimes in which the formation of a dipolar vortex is forbidden. For a large perpendicular ion velocity shear parameter, a counter-rotating vortex is similar to a vortex chain. The newly found counter-rotating vortex can be correlated with coherent nonlinear structures that are observed in association with sheared plasma flows in space and laboratory environments.
Abstract: It is shown that sheared plasma flows can generate nonthermal electrostatic waves in a magnetized dusty electron-positron plasma. Linearly excited modes attain large amplitudes and start interacting among themselves. Nonlinearly coupled modes self-organize in the form of coherent vortices comprising a vortex chain and a double vortex. Conditions under which the latter appear are given. The relevance of our investigation to space, astrophysical, and laboratory plasmas is pointed out.
Abstract: Low-frequency electrostatic dust-modes are theoretically investigated accounting for dust grain charge fluctuation and for equilibrium grain charge inhomogeneity in a strongly coupled dusty plasma. A new stable extremely low-frequency mode, which is due to the inhomogeneity in the equilibrium dust grain charge, is found to exist in such a dusty plasma. It is also found that the dust-acoustic mode becomes unstable due to the effect of this equilibrium dust grain charge inhomogeneity. It is observed here that the influence of strong correlations in the dust fluid significantly modify the dispersion properties of this new mode as well as of the existing dust-acoustic mode. The implications of our results to recent experimental observations and to some space and astrophysical situations are briefly discussed. (C) 2000 American Institute of Physics. [S1070-664X(00)02606-9].
Abstract: The electromagnetic effects are incorporated in the study of toroidal ion-temperature-gradient (ITG) modes in a nonuniform magnetoplasma. For this purpose, dispersion relations have been derived by employing the fluid and gyrokinetic responses for the ions, as well as the fluid electron response along with Ampere's law. The dispersion relations are numerically analyzed and results for the real and imaginary parts of the ITG wave frequencies are displayed for different values of epsilon(n) = 2L(n)/L-B (where L-n and L-B are the characteristic scale lengths of the density and magnetic field gradients, respectively) and lambda(i parallel to) = k(parallel to)lambda(i), where k(parallel to) is the parallel component of the wave vector and lambda(i) is the collisionless ion skin depth. It is found that electromagnetic effects are stabilizing. Furthermore, also presented are brief calculations of particle as well as ion thermal transports in the presence of nonthermal electromagnetic fluctuations. The relevance of this investigation to the plasma confinement in tokamaks is discussed. (C) 2000 American Institute of Physics. [S1070-664X(00)02704-X].
Abstract: The nonlinear interaction between broadband Langmuir waves and electrostatic dust-acoustic perturbations in a uniform collisional dusty plasma is considered, taking into account the combined effects of the Langmuir wave ponderomotive force and the electron Joule heating nonlinearity. This coupling is governed by a Liouville equation for a Langmuir wave packet and an equation for a dust-acoustic perturbation that is driven by the ponderomotive and thermal forces of the random phase Langmuir waves. The mode coupling equations are then Fourier decomposed to derive the nonlinear dispersion relation. The latter is analyzed numerically for a Gaussian Langmuir wave spectrum, by taking parameters that are relevant for low-temperature dusty plasma discharges. It is found that a broadband spectrum of Langmuir waves is subjected to a rapidly growing modulational instability in a dusty plasma. (C) 2000 American Institute of Physics. [S1070-664X(00)02511-8].
Abstract: Spontaneous magnetic fields are generated due to non-parallel density and temperature gradients in dusty plasmas and can modify the dynamics of the dusty systems. They are maintained if there exists some plasma vorticity. We employ a kinetic model and use the Hamiltonian approach, in order to present a class of stationary nonlinear dusty plasma equilibria. where the plasma number density, the scalar potential, the plasma current density, and the magnetic field are shown. This may provide a better understanding of stationary dusty laboratory plasmas.
Abstract: It is shown that sheared electron flows can generate long as well as short wavelength (in comparison with the ion gyroradius) electrostatic waves in a nonuniform magnetplasma. For this purpose, we derive dispersion relations by employing two-fluid and hybrid models; in the two-fluid model the dynamics of both the electrons and ions are governed by the hydrodynamic equations and the guiding center fluid drifts, whereas the hybrid model assumes kinetic ions and fluid electrons. Explicit expressions for the growth rates and thresholds are presented. Linearly excited waves attain finite amplitudes and start interacting among themselves. The interaction is governed by the nonlinear equations containing the Jacobian nonlinearities. Stationary solutions of the nonlinear mode coupling equations can be represented in the form of a dipolar vortex and a vortex street. Conditions under which the latter arise are given. Numerical results for the growth rates of linearly excited modes as well as for various types of vortices are displayed for the parameters that are relevant for the F-region of the Earth's ionosphere. It is suggested that the results of the present investigation are useful in understanding the properties of nonthermal electrostatic waves and associated nonlinear vortex structures in the Earth's ionosphere. (C) 2000 Elsevier Science Ltd. All rights reserved.
Abstract: The nonlinear coupling between broadband-upper-hybrid (BBUH) waves and electrostatic ion-cyclotron perturbations in a uniform collisional magnetoplasma is considered, taking into account the combined effects of the UH ponderomotive and thermal nonlinear forces. This coupling is governed by a pair of equations which is employed to derive the nonlinear dispersion relation, which admits modulational instabilities of BBUH waves in some interesting cases. The relevance of our investigation to the nonlinear propagation of random phase upper-hybrid waves in a weakly collisional Earth's ionosphere as well as in low-temperature laboratory discharges is pointed out.
Abstract: It is shown that nonparallel density and temperature gradients can produce magnetic fields in dusty plasmas. Spontaneously created magnetic fields can be maintained if there exists plasma vorticity. In order to understand this phenomena, a self-consistent dusty plasma equilibrium model is constructed by employing a kinetic description and invoking the Hamiltonian approach. Stationary nonlinear dusty plasma equilibria contain specific profiles for the plasma number density, the plasma current, and the magnetic field. The relevance of this investigation to low-temperature laboratory dusty and space plasmas is discussed. (C) 1999 American Institute of Physics. [S1070-664X(99)01407-X].
