The equation of polarization transfer in an inhomogeneous magnetized plasma

Recently we have derived the equation of polarization transfer in an inhomogeneous magnetized plasma in the case where absorption is so weak that the characteristic modes can be considered to be orthogonal. We extend this investigation to the study of polarization transfer in a plasma where the characteristic polarizations need not be orthogonal. We obtain explicit expressions for the Faraday rotation tensor, the absorption tensor, the mode-coupling tensor and the tensor describing the explicit spatial variation of characteristic polarizations due to plasma inhomogeneity.     

The interaction of an obliquely incidents-polarized plane electromagnetic wave at a warm moving magnetized plasma half-space

The interaction of ans-polarized plane electromagnetic wave incident from a dielectric (or vacuum) region on awarm moving magnetized plasma half-space is considered. The external magnetic field is assumed to be normal to the direction of the wave normal and the velocity of the moving medium. Using the first three moment equations, together with Maxwell's electromagnetic equations, we construct the constitutive relations in the rest frame of the moving medium. The constitutive relations are then transformed to the laboratory frame by invokingMinkowski's equations for the moving plasma medium, and the dispersion relation for the propagating ordinary mode in the moving medium is derived. Expressions are obtained for the phase and group velocities and the index of refraction for the ordinary mode, as also for power reflection and transmission coefficients. It is found that in contrast to the case of a cold magnetized plasma, the ordinary electromagnetic mode excited in the warm magnetoplasma medium getsmodified due to the presence of an external magnetic field. In addition, the various reflection and transmission characteristics for a warm magnetoplasma depend on the velocity of the moving plasma as well as on the strength of the applied magnetic field, as against the case for a cold moving magnetized plasma. Numerical results on the reflection coefficient are presented for several values of the parameters characterizing the electron-plasma temperature, the velocity of the moving medium and the strength of the applied magnetic field.     

Current gradient-driven linear and nonlinear electromagnetic waves in a magnetized electron-positron plasma

A set of coupled nonlinear differential equations which govern the dynamics of finite amplitude electromagnetic waves in the presence of an external current gradient in a magnetized electron-positron plasma has been derived. It is shown that the current gradient can make shear Alfvén-like waves unstable. A quasi-stationary solution of the mode-coupling equations is the well-localized dipole vortex. Application of our results to plasma transport in the pulsar magnetosphere is briefly discussed.     

Hot plasma waves surrounding the Schwarzschild event horizon in a Veselago medium

This paper investigates wave properties of hot plasma in a Veselago medium. For the Schwarzschild black hole, the 3+1 GRMHD equations are re-formulated which are linearly perturbed and then Fourier analyzed for rotating (non-magnetized and magnetized) plasmas. The graphs of wave vector, refractive index and change in refractive are used to discuss the wave properties. The results obtained confirm the presence of Veselago medium for both rotating (non-magnetized and magnetized) plasmas. This work generalized the isothermal plasma waves in the Veselago medium to hot plasma case.     

Dispersion and stability of waves in plasmas in the presence of a coriolis force

The dispersion law for the propagation of waves in cold magnetized plasmas is derived for arbitrary directions of the rotation axis with respect to the static magnetic field. The waves are shown to be stable, not only in the case of a cold plasma, but in any plasma case which yields hermitian mobility tensors. An interesting special case is when the rotation and magnetization axes are parallel, because then for suitable values of rotation and external magnetic field the two effects can cancel each other, though only for one plasma species at the time. The rotation thus decisively affects and shifts the number and width of the existing pass- and stop-bands in a magnetized plasma. The inclusion of thermal effects through a scalar barotropic pressure is not nearly as significant.     

Polarization transfer in a pulsar magnetosphere

Propagation of radio waves in the ultrarelativistic magnetized electron–positron plasma of a pulsar magnetosphere is considered. The polarization state of the original natural waves is found to vary markedly on account of the wave mode coupling and cyclotron absorption. The change is most pronounced when the regions of mode coupling and cyclotron resonance approximately coincide. In cases when the wave mode coupling occurs above and below the resonance region, the resultant polarization appears essentially distinct. The main result of the paper is that in the former case the polarization modes become non-orthogonal. The analytical treatment of the equations of polarization transfer is accompanied by numerical calculations. The observational consequences of polarization evolution in pulsar plasma are discussed as well.     

Nonlinear convective motion in a rotating magnetized electron-positron plasma

A set of coupled nonlinear equations is derived which describes the coupling of the vorticity and the external-field aligned flow of a strongly magnetized rotating electron-positron plasma. The possibility of dipole vortex formation is discussed.     

Gravitational stability of finitely conducting two-component plasma through porous medium

The gravitational stability of magnetized self-gravitating two-component plasma of finite conductivity flowing through porous medium is studied. Effect of magnetic field, porosity, viscosity, finite conductivity, and neutral gas friction is considered on the stability of the system. Dispersion relations are derived from linearized equations using normal mode analysis. Longitudinal and transverse wave propagations are discussed. On the basis of Hurwitz criterion, the stability of the system is discussed. It is found that Jeans's criterion determines the stability of the system. Jeans's expression depends on the sonic speeds in both the components. For transverse wave propagation in perfectly conducting plasma. Jeans's expression is modified due to magnetic field and porosity but in case of finitely conducting plasma the Jeans's expression remains unaltered. Collisional frequency, viscosity, permeability of the porous medium have damping effect.     

Self-organization of electromagnetic waves into vortices in a magnetized electron-positron plasma

This paper presents a new class of well localized dipolar vortex solutions to the newly derived set of coupled nonlinear equations governing the dynamics of low-frequency electromagnetic waves in a strongly magnetized electron-positron plasma.     

Nonlinear properties of electron acoustic wave turbulence in the geomagnetic tail

The nonlinear properties of electron acoustic waves in a magnetized plasma consisting of hot electrons, hot ions, and cold electrons are investigated. Using a fluid-guiding center model for the cold electrons and Boltzmann distributions for the hot species, a set of nonlinear mode-coupling equations is derived. Monopole and dipole-vortex solutions are shown to exist for the system of nonlinear equations. Spectrum cascade by mode-coupling in the electron acoustic wave turbulence is investigated. Relevance of our investigation to broadband electrostatic noise (BEN) in the geomagnetic tail is discussed.     

Strong electromagnetic waves in a magnetized relativistic electron-positron plasma

It is shown that in a strongly magnetized relativistic electron-positron plasma, strongly localized large amplitude circularly polarized electromagnetic wave pulses exist. The localization is due to relativistic mass variation as well as ponderomotive force effects. Three types of pulses are found analytically: the sharply spiked pulse in a strongly magnetized cold plasma, the smooth pulse in a week magnetized warm plasma, and the moderately spiked pulse for a weakly magnetized cold plasma. The physical mechanisms giving rise to these pulses are distinct for each case. Possible implications of our investigation to pulsar radiation are discussed.     

Higher-order Zakharov–Kuznetsov equation for dust-acoustic solitary waves with dust size distribution

Nonlinear propagating dust-acoustic solitary waves (DASWs) in a warm magnetized dusty plasma containing different size and mass negatively charged dust particles, isothermal electrons, high- and low-temperature ions are investigated. For this purpose, a reasonable normalization of the hydrodynamic and Poisson equations is used to derive the Zakharov–Kuznetsov (ZK) equation for the first-order perturbed potential. As the wave amplitude increases, the width and the velocity of the solitons deviate from the prediction of the ZK equation, i.e., the breakdown of the ZK approximation. To describe the soliton of larger amplitude, a linear inhomogeneous Zakharov-Kuznetsov-type (ZK-type) equation for the second-order perturbed potential is derived. Stationary solutions of both equations are obtained using the renormalization method. Numerically, the effect of power law distribution on the higher-order corrections is examined. It is found that the soliton amplitude in case of power law distribution is smaller than that of monosized dust grains. The higher-order corrections play a role to reduce the strength of the nonlinearity for power law distribution case. The relevance of the present investigation to Saturn's F-ring and laboratory experiment is discussed.     

Atmospheres and spectra of strongly magnetized neutron stars

We construct atmosphere models for strongly magnetized neutron stars with surface fields     and effective temperatures     . The atmospheres directly determine the characteristics of thermal emission from isolated neutron stars, including radio pulsars, soft gamma-ray repeaters, and anomalous X-ray pulsars. In our models, the atmosphere is composed of pure hydrogen or helium and is assumed to be fully ionized. The radiative opacities include free–free absorption and scattering by both electrons and ions computed for the two photon polarization modes in the magnetized electron–ion plasma. Since the radiation emerges from deep layers in the atmosphere with     , plasma effects can significantly modify the photon opacities by changing the properties of the polarization modes. In the case where the magnetic field and the surface normal are parallel, we solve the full, angle-dependent, coupled radiative transfer equations for both polarization modes. We also construct atmosphere models for general field orientations based on the diffusion approximation of the transport equations and compare the results with models based on full radiative transport. In general, the emergent thermal radiation exhibits significant deviation from blackbody, with harder spectra at high energies. The spectra also show a broad feature     around the ion cyclotron resonance     , where Z and A are the atomic charge and atomic mass of the ion, respectively; this feature is particularly pronounced when     . Detection of the resonance feature would provide a direct measurement of the surface magnetic fields on magnetars.     

Nonlinear coupling between electromagnetic fields in a strongly magnetized electron-positron plasma

The nonlinear coupling between electromagnetic fields in a strongly magnetized electron-positron plasma is considered. We point out that compressional magnetic field perturbations are excited by the rotational part of the nonlinear current, and derive a new nonlinear system of equations that is basic for studies of modulational instabilities and coherent nonlinear structures in magnetized electron-positron plasmas.     

Electrostatic drift vortices in a hot rotating strongly magnetized electron-positron pulsar plasma

Electrostatic drift wave in a hot rotating and strongly magnetized electron-positron pulsar plasma is considered. Using relativistic two fluid equations a pair of coupled nonlinear equations is derived. It is shown that the wave can propagate in the form of two-dimensional dipolar vortices at ultrarelativistic temperature (Tmc ²) of the plasma. The latter may affect the energy transport in the hot plasma, which can lead to a new turbulent state in the pulsar magnetosphere.     

Nonlinear Drift-Alfvén Waves in Relativistically Hot Nonuniform Electron-Positron Plasmas

The magnetic viscosity tensor is derived for a magnetized relativistic collisionless plasma with temperature gradients. By means of this tensor we deduce the nonlinear equations for drift–Alfvén waves in a relativistic electron-positron low plasma with density and temperature gradients. It is shown that our new equations have solutions in the form of dipolar vortices. The present results should be relevant to a number of astrophysical objects with strong electron-positron pair production, e.g. in pulsars as well as in accretion disks and jets.     

Effects of plasma rotation on alfvén solitons in pulsar magnetospheres

Nonlinear Alfvén wave in a hot rotating and strongly magnetized electron-positron plasma is considered. Using relativistic two fluid equations, the dispersion relation for Alfvén wave in the rotating plasma is obtained. Large amplitude Alfvén solitons are found to exist in the rotating pulsar plasma. Rotational effects on solitons are discussed.     

Hot plasma waves in Schwarzschild magnetosphere

In this paper we examine the wave properties of a hot plasma living in a Schwarzschild magnetosphere. The 3+1 GRMHD perturbation equations are formulated for this scenario. These equations are Fourier analyzed and then solved numerically to obtain the dispersion relations for a non-rotating, rotating non-magnetized and rotating magnetized plasma. The wave vector is evaluated, which is used to calculate the refractive index. These quantities are shown in graphs which are helpful to discuss the dispersive properties of the medium near the event horizon.     

Oblique collision effects on nonlinear quantum dust-acoustic solitary waves in magnetized dense dusty plasmas

The oblique collision of nonlinear quantum dust-acoustic (NQDA) solitary waves in a three-dimensional (3D) magnetized dense dusty plasma is investigated. Furthermore, two coupled Kortwege–de Vries equations for describing our model and the analytical phase shifts after the oblique collision of two NQDA solitary waves are derived using the extended Poincaré–Lighthill–Kuo (PLK) method. The modification in the phase shift and the trajectory of the NQDA solitary waves structures due to the inclusion of oblique collision and external magnetic field are discussed numerically. The numerical results are applied to high density astrophysical situations such as in superdense white dwarfs.