Propagation regimes for an electromagnetic beam in magnetized plasma

The propagation of a Gaussian electromagnetic beam along the direction of magnetic field in a plasma is investigated. The extraordinary (E-x+iE(y)) mode is explicitly considered in the analysis, although the results for the ordinary mode can be obtained upon replacing the electron cyclotron frequency omega(c) by -omega(c). The propagating beam electric field is coupled to the surrounding plasma via the dielectric tensor, taking into account the existence of a stationary magnetic field. Both collisionless and collisional cases are considered, separately. Adopting an established methodological framework for beam propagation in unmagnetized plasmas, we extend to magnetized plasmas by considering the beam profile for points below the critical curve in the beam-power versus beam-width plane, and by employing a relationship among electron concentration and electron temperature, provided by kinetic theory (rather than phenomenology). It is shown that, for points lying above the critical curve in the beam-power versus beam-width plane, the beam experiences oscillatory convergence (self-focusing), while for points between the critical curve and divider curve, the beam undergoes oscillatory divergence and for points on and below the divider curve the beam suffers a steady divergence. For typical values of parameters, numerical results are presented and discussed. (C) 2008 American Institute of Physics.

Experimental realisation of electromagnetic metamaterials

By engineering the internal structure of artificial materials it is possible to reproduce effective electromagnetic properties, including some which were previously unavailable in nature. Since the first experimental demonstration of artificial composites with exotic electromagnetic properties at microwaves less than 10 years ago, metamaterials has emerged as a rapidly growing multidisciplinary branch of science and engineering. Significant efforts have been placed in scaling the response of metamaterials to optical frequencies as well as demonstrate pertinent applications of the newly available technology. In this article we review recent developments in the area of experimental realisation of electromagnetic metamaterials and their applications.

Electromagnetic interaction between a metallic nanoparticle and surface in tunnelling proximity-modelling and experiment

We simulate the localized surface plasmon resonances of an Au nanoparticle within tunnelling proximity of an Au substrate. The results demonstrate that the calculated resonance energies can be identified with those experimentally detected for light emission from the tip-sample junction of a scanning tunnelling microscope. Relative to the modes of an isolated nanoparticle these modes show significant red-shifting, extending further into the infrared with increasing radius, primarily due to a proximity-induced lowering of the effective bulk plasmon frequency. Spatial mapping of the field enhancement factor shows an oscillatory variation of the field, absent in the case of a dielectric substrate; also the degree of localization of the modes, and thus the resolution achievable electromagnetically, is shown to depend primarily on the nanoparticle radius, which is only weakly dependent on wavelength.

Proton moire fringes for diagnosing electromagnetic fields in opaque materials and plasmas

High contrast proton moire fringes have been obtained in a laser-produced proton beam. Moire u fringes with modulation of 20%-30% were observed in protons with energies in the range of 4 - 7 MeV. Monte Carlo simulations with simple test fields showed that shifts in the moire u fringes can be used to give quantitative information on the strength of transient electromagnetic fields inside plasmas and materials that are opaque to conventional probing methods. (C) 2003 American Institute of Physics.

Low-frequency electromagnetic waves in a Hall-magnetohydrodynamic plasma with charged dust macroparticles

A linear theory for intermediate-frequency [much smaller (larger) than the electron gyrofrequency (dust plasma and dust gyrofrequencies)], long wavelength (in comparison with the ion gyroradius and the electron skin depth) electromagnetic waves in a multicomponent, homogeneous electron-ion-dust magnetoplasma is presented. For this purpose, the generalized Hall-magnetohydrodynamic (GH-MHD) equations are derived for the case with immobile charged dust macroparticles. The GH-MHD equations in a quasineutral plasma consist of the ion continuity equation, the generalized ion momentum equation, and Faraday's law with the Hall term. The GH-MHD equations are Fourier transformed and combined to obtain a general dispersion relation. The latter is analyzed to understand the influence of immobile charged dust grains on various electromagnetic wave modes in a magnetized dusty plasma. (C) 2005 American Institute of Physics.

Envelope solitons associated with electromagnetic waves in a magnetized pair plasma

The amplitude modulation of magnetic field-aligned circularly polarized electromagnetic (CPEM) waves in a magnetized pair plasma is reexamined. The nonlinear frequency shifts include the effects of the radiation pressure driven density and compressional magnetic field perturbations as well as relativistic particle mass variations. The dynamics of the modulated CPEM wave packets is governed by a nonlinear Schrodinger equation, which has attractive and repulsive interaction potentials for fast and slow CPEM waves. The modulational stability of a constant amplitude CPEM wave is studied by deriving a nonlinear dispersion from the cubic Schrodinger equation. The fast (slow) CPEM mode is modulationally unstable (stable). Possible stationary amplitude solutions of the modulated fast (slow) CPEM mode can be represented in the form of bright and dark/gray envelope electromagnetic soliton structures. Localized envelope excitations can be associated with the microstructures in pulsar magnetospheres and in laboratory pair magnetoplasmas. (C) 2005 American Institute of Physics.

Nonlinear propagation of electromagnetic waves in negative-refraction-index composite materials

We investigate the nonlinear propagation of electromagnetic waves in left-handed materials. For this purpose, we consider a set of coupled nonlinear Schrodinger (CNLS) equations, which govern the dynamics of coupled electric and magnetic field envelopes. The CNLS equations are used to obtain a nonlinear dispersion, which depicts the modulational stability profile of the coupled plane-wave solutions in left-handed materials. An exact (in)stability criterion for modulational interactions is derived, and analytical expressions for the instability growth rate are obtained.

Dynamics of nonlinearly coupled magnetic-field-aligned electromagnetic electron-cyclotron waves near the zero-group-dispersion point in magnetized plasmas

The nonlinear coupling between two magnetic-field-aligned electromagnetic electron-cyclotron (EMEC) waves in plasmas is considered. Evaluating the ponderomotive coupling between the EMEC waves and quasistationary plasma density perturbations, a pair of coupled nonlinear Schrodinger equations (CNLSEs) is obtained. The CNLSEs are then used to investigate the occurrence of modulational instability in magnetized plasmas. Waves in the vicinity of the zero-group-dispersion point are considered, so that the group dispersion terms may either bear the same or different signs. It is found that a stable EMEC wave can be destabilized due to its nonlinear interactions with an unstable one, while a pair of unstable EMEC waves yields an increased instability growth rate. Individually stable waves remain stable while interacting with one another. Stationary nonlinear solutions of the coupled equations are presented. The relevance of our investigation to nonlinear phenomena in space plasmas is discussed. (c) 2005 American Institute of Physics.