Magnetic Electron Drift Vortex Research Articles

Coupling of magnetic electron drift vortex mode with longitudinal perturbations in collision-less and dissipative electron and electron-ion plasmas

The plasma density non-uniformity gives rise to the coupling of transverse magnetic electron drift vortex (MEDV) mode with the longitudinal perturbations in dissipative and non-dissipative electron plasmas. This coupling produces partially transverse and partially longitudinal low frequency instabilities in classical un-magnetized laser plasmas. The MEDV mode couples with the ion acoustic wave, when the ion dynamics is also included. Both the modes have frequencies of the same order of magnitude and couple to give rise to electromagnetic instabilities in un-magnetized plasmas.

Magnetic electron-drift vortex modes in an inhomogeneous quantum plasma

AbstractDispersion relation for the low-frequency magnetic electron-drift vortex (MEDV) mode in an inhomogeneous dense quantum plasma has been derived. New class of purely growing instabilities are found to exist on a time scale of the order of ion plasma period. We found that the MEDV mode become unstable when the propagation direction is perpendicular to the equilibrium density gradients. We believe that the present investigation would be useful to understand the wave phenomena and in the study of magnetic field generation in laser-produced plasmas as well as in dense space plasmas, where quantum effects are expected to play a dominant role.

Numerical study of the magnetic electron drift vortex mode turbulence in a nonuniform magnetoplasma

A simulation study of the magnetic electron drift vortex (MEDV) mode turbulence in a magnetoplasma in the presence of inhomogeneities in the plasma temperature and density, as well as in the external magnetic field, is presented. The study shows that the influence of the magnetic field inhomogeneity is to suppress streamerlike structures observed in previous simulation studies without background magnetic fields. The MEDV mode turbulence exhibits nonuniversal (non-Kolmogorov-type) spectra for different sets of the plasma parameters. In the presence of an inhomogeneous magnetic field, the spectrum changes to a 7/3 power law, which is flatter than without magnetic field gradients. The relevance of this work to laser-produced plasmas in the laboratory is briefly mentioned.

Dynamics of nonlinearly interacting magnetic electron drift vortex modes in a nonuniform plasma

A simulation study of dynamical evolution of nonlinearly interacting two-dimensional magnetic electron drift vortex (MEDV) modes in a nonuniform plasma is presented. Depending on the equilibrium density and temperature gradients, the system can either be stable or unstable. The unstable system reveals spontaneous generation of magnetic fields from noise level, and large-scale magnetic field structures are formed. When the system is linearly stable, one encounters MEDV mode turbulence in which there is a competition between zonons (zonal flows) and streamers. For large MEDV mode amplitudes, one encounters the formation of localized and small-scale magnetic vortices and vortex pairs with scale sizes of the order of the electron skin depth. The MEDV turbulence exhibits nonuniversal (non-Kolmogorov-type) spectra for different sets of plasma parameters. The relevance of this work to laboratory and cosmic plasmas is briefly mentioned.

Simulations of two-dimensional magnetic electron drift vortex mode turbulence in plasmas

AbstractSimulations are performed to investigate the turbulent properties of nonlinearly interacting two-dimensional magnetic electron drift vortex (MEDV) modes in a non-uniform unmagnetized plasma. The relevant nonlinear equations governing the dynamics of the MEDV modes are the wave magnetic field and electron temperature perturbations in the presence of the equilibrium density and temperature gradients. The important nonlinearities come from the advection of the electron fluid velocity perturbation and the electron temperature, as well as from the nonlinear electron Lorentz force. Computer simulations of the governing equations for the nonlinear MEDV modes reveal the generation of streamer-like electron flows, such that the corresponding gradients in the direction of the inhomogeneities tend to flatten out. In contrast, the gradients in an orthogonal direction vary rapidly. Consequently, the inertial range energy spectrum in decaying MEDV mode turbulence exhibits a much steeper anisotropic spectral index. The magnetic structures in the MEDV mode turbulence produce non-thermal electron transport in our non-uniform plasma.

Electron magnetohydrodynamics of inhomogeneous plasmas

A description of electron magnetohydrodynamics (EMHD) in nonuniform warm resistive plasmas with equilibrium density, velocity, and electron temperature gradients is presented. For this purpose, a pair of of equations, which show the linear and nonlinear couplings between magnetic electron drift vortex modes and obliquely propagating electron whistlers, is derived and analyzed.

Order and chaos in the magnetic electron drift vortex mode

Ordered structures as well as chaotic motion of the magnetic electron drift vortex (MEDV) mode in a unmagnetized nonuniform plasma are discussed. In the collisionless limit, the nonlinear MEDV waves can self-organize into dipolar vortices or vortex chains. The latter exist in the regime where dipolar vortices are forbidden. When dissipation is included, the governing equations for the MEDV mode can be cast into the form of the Lorenz equations, so that chaotic solutions can exist.

Magnetic electron drift vortex in magnetized plasma

The Magnetic Electron Drift Vortex (MEDV) modes in a homogeneous magnetized plasma are investigated using the Braginskii's fluid model for electrons. It is found that the modes become unstable when the propagation is in both parallel and perpendicular directions with respect to density and temperature gradients. The instability characteristics of the mode are presented by analyzing it analytically as well as numerically. The relevance to wave phenomena in space and laboratory plasmas is pointed out.

Theory of magnetic field generation.

It is pointed out that fluctuating magnetic fields are generated on an ion time scale in laser-induced plasmas in the limit \ensuremath{\omega}\ensuremath{\ll}${\mathrm{\ensuremath{\omega}}}_{\mathit{pe}}$ where \ensuremath{\omega} is the perturbation frequency and ${\mathrm{\ensuremath{\omega}}}_{\mathit{pe}}$ is the electron plasma oscillation frequency. It is not the electron temperature perturbation that is crucial for the so-called magnetic electron drift vortex modes, as has been suggested previously. Some different electromagnetic and purely magnetic perturbations near the ion acoustic wave frequency in nonuniform plasmas have been proposed to be responsible for the generation of B fields. In the high-frequency range, propagation parallel to external gradients can give rise to instabilities of the radiation modes. \textcopyright{} 1996 The American Physical Society.

Anomalous electron energy transport by two-dimensional MEDV modes

It is found that the magnetic electron drift vortex (MEDV) modes can cause anomalous electron energy transport in collisionless non-uniform unmagnetized plasmas. An expression for the thermal conductivity is obtained using a quasilinear approach. The instabilities of MEDV modes, which previously were believed to be stable surface oscillations, and the associated thermal conductivity depends upon the component of wave vector in the direction of inhomogeneities. Some instabilities of magnetic perturbations previously predicted to exist in dissipative laser-produced plasmas are shown to be unrealistic. The results may be useful in the study of laser-produced as well as other plasmas.

Magnetic electron drift vortex mode instability in a cylindrical plasma

An equation describing the propagation and instability behavior of magnetic electron drift vortex modes in a cylindrically symmetric rotating plasma is derived without using the local approximation. The effects of equilibrium density, velocity, and temperature, as well as magnetic field gradients, are included. An approximate analytical solution for modes near the center of the plasma is obtained.

Magnetic Electron Drift Vortex Modes in General Equilibria

AbstractThe equation and dispersion relation describing the magnetic electron drift vortex mode in a generalized equilibrium are presented. The results are useful for investigating related surface wave problems as well as for identifying the various forms of the magnetic electron drift vortex mode.

Linear and Nonlinear Magnetic Electron Drift Waves in a Nonuniform Strong Magnetic Field

AbstractLinear and nonlinear propagation of magnetic electron drift vortex waves in a nonuniform magnetic field is investigated by means of a generalized adiabatic law which takes into account the effect of strong fields and reduces in the appropriate limits to several well known energy conservation equations in a collisionless plasma. In the linear limit, an instability is shown to exist, whereas in the nonlinear regime, steady‐state dipole vortices associated with the electron drift vortex waves may appear. The anomalous electron energy transport associated with the unstable magnetic electron drift vortex waves is investigated by means of a quasilinear theory.

Anomalous heat flux due to magnetic electron-drift vortex waves in a magnetized plasma.

The magnetic electron-drift vortex mode in a magnetized plasma is investigated using the Braginskii transport equations for the electrons. In a sufficiently inhomogeneous external magnetic field, the mode can become unstable, causing enhanced local magnetic fluctuations. The latter give rise to an anomalous electron thermal flux that significantly affects the transport characteristics of the plasma. Using the conventional quasilinear approach, the corresponding anomalous thermal conductivity is obtained.

Electron energy transport by magnetic electron drift vortex waves

It is shown that magnetic electron drift vortex waves can cause electron energy transport in a nonuniform plasma. Using a quasilinear approach, an expression for the corresponding anomalous thermal conductivity is derived. The result may be relevant to the study of energy transport in laser-produced as well as other plasmas.

Kinetic theory of electron drift vortex modes

Magnetic electron drift vortex modes are examined using a kinetic theory. The dispersion is found to be much different than that obtained from the fluid theory. For frequencies much smaller than the electron plasma frequency, the waves are heavily Landau damped. The modes are weakly damped at frequencies just below the plasma frequency and hence have an electromagnetic rather than magnetic character.

Parametric excitation of magnetic electron drift vortex modes by Langmuir waves

A new multi-dimensional parametric interaction coupling Langmuir waves with magnetic electron drift vortex modes is presented. A general dispersion relation for the parametric instabilities is derived, and the growth rates of the decay and modulational instabilities are obtained. The present instabilities can be the source of large-scale magnetic fields near the critical surface of a laser-produced plasma.