Equations for a plasma consisting of matter and antimatter

A set of fluid type equations is derived to describe the macroscopic behaviour of a plasma consisting of a mixture of matter and antimatter. The equations are written in a form which displays the full symmetry of the medium with respect to particle charge and mass, a symmetry absent in normal plasmas. This symmetry of the equations facilitates their manipulation and solution, and by way of illustration the equations are used to analyze the propagation of electromagnetic and acoustic waves through a matter-antimatter plasma. Some differences from the propagation of such waves in a normal plasma are noted.     

Non-linear damping of visco-resistive Alfvén waves in solar spicules

Interaction of Alfvén waves with plasma inhomogeneities generates phase mixing which can lead to dissipate Alfvén waves and to heat the solar plasma. Here we study the dissipation of Alfvén waves by phase mixing due to viscosity and resistivity variations with height. We also consider nonlinear magnetohydrodynamic (MHD) equations in our theoretical model. Non-linear terms of MHD equations include perturbed velocity, magnetic field, and density. To investigate the damping of Alfvén waves in a stratified atmosphere of solar spicules, we solve the non-linear MHD equations in the x–z plane. Our simulations show that the damping is enhanced due to viscosity and resistivity gradients. Moreover, energy variations is influenced due to nonlinear terms in MHD equations.     

Reflection Properties of Gravito-MHD Waves in an Inhomogeneous Horizontal Magnetic Field

We derive the dispersion equation for gravito-magnetohydrodynamical (MHD) waves in an isothermal, gravitationally stratified plasma with a horizontal inhomogeneous magnetic field. Sound and Alfvén speeds are constant. Under these conditions, it is possible to derive analytically the equations for gravito-MHD waves. The high values of the viscous and magnetic Reynolds numbers in the solar atmosphere imply that the dissipative terms in the MHD equations are negligible, except in layers around the positions where the frequency of the MHD wave equals the local Alfvén or slow wave frequency. Outside these layers the MHD waves are accurately described by the equations of ideal MHD. We consider waves that propagate energy upward in the atmosphere. For the plane boundary, z=0, between two isothermal plasma regions with horizontal but different magnetic fields, we discuss the boundary conditions and derive the equations for the reflection and transmission coefficients. In the simpler case of a gravitationally stratified plasma without magnetic field, these coefficients describe the reflection and transmission properties of gravito-acoustic waves.     

Alfvén-magnetosonic waves interaction in the solar corona

The nonlinear propagation of the Alfvén and magnetosonic waves in the solar corona is investigated in terms of model equations. Due to viscous effects taken into account the propagation of the fast wave itself is governed by Burgers type equations possessing both expansion and compression shock solutions. Numerical simulations show that both parallely and perpendicularly propagating fast waves can steepen into shocks if their amplitudes are in excess of some sizeable fraction of the Alfvén velocity. However, if the magnetic field changes linearly in the perpendicular direction, then formation of perpendicular shocks can be hindered. The Alfvén waves exhibit a tendency to drive both the slow and fast magnetosonic waves whose propagation is described by linearized Boussinesq type equations with ponderomotive terms due to the Alfvén wave. The limits of the slow and fast waves are investigated.     

Alfven waves and magneto-sensitive lines

In this paper the equations of transfer of Stokes parameters are solved under the hypothesis of the propogation of Alfven waves. The effects of Alfven waves on the magneto-sensitive line FeIλ6302. 499 in the spectra of sunspots are calculated. Besides, some methods have been proposed for the verification of theoretical computations with observational material and for estimating the energy flux of Alfven waves.     

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.     

Parametric coupling between electromagnetic ion-cyclotron and shear Alfvén waves

The nonlinear interaction between finite amplitude electromagnetic ion-cyclotron waves and shear-Alfvén waves is considered. It is shown that this process is governed by three coupled equations. They are here used to study modulational instabilities. The relevance of our investigation to low-frequency electromagnetic fluctuations in space plasmas is pointed out.     

Parametric instabilities and nucleation of coupled Langmuir and acoustic waves in a weakly-ionized plasma

A pair of coupled equations governing the nonlinear interaction between Langmuir and acoustic waves in partially-ionized plasmas are presented. Three-wave decay interactions, modulatinal instabilities, as well as the nucleation of coupled Langmuir and acoustic waves can then be studied. The results are of relevance to the lower part of the ionosphere, radio-frequency driven gas discharges, as well as the interstellar medium.     

A numerical method of studying the evolution of spherically symmetric superdense celestial bodies

For fully relativistic strong gravitational fields we obtain a consistent set of hydrodynamic and field equations that describe the propagation of all types of waves in matter (from small perturbations to shock waves). We obtain an algorithm for numerical solution of these equations for certain equations of state of degenerate matter.Translated fromAstrofizika, Vol. 37, No. 4, 1994.We are very grateful to Prof. Chubarian for valuable instructions and discussions. The work of A. Sadoyan was sponsored in part by ISF grant RYG000.     

Effects of the non-extensive parameter on the propagation of ion acoustic waves in five-component cometary plasma system

Some important evolution nonlinear partial differential equations are derived using the reductive perturbation method for unmagnetized collisionless system of five component plasma. This plasma system is a multi-ion contains negatively and positively charged Oxygen ions (heavy ions), positive Hydrogen ions (lighter ions), hot electrons from solar origin and colder electrons from cometary origin. The positive Hydrogen ion and the two types of electrons obey \(q\)-non-extensive distributions. The derived equations have three types of ion acoustic waves, which are soliton waves, shock waves and kink waves. The effects of the non-extensive parameters for the hot electrons, the colder electrons and the Hydrogen ions on the propagation of the envelope waves are studied. The compressive and rarefactive shapes of the three envelope waves appear in this system for the first order of the power of the nonlinearity strength with different values of non-extensive parameters. For the second order, the strength of nonlinearity will increase and the compressive type of the envelope wave only appears.     

Magnetohydrodynamics in superconducting-superfluid neutron stars

Magnetohydrodynamic (MHD) equations are presented for the mixture of superfluid neutrons, superconducting protons and normal electrons believed to exist in the outer cores of neutron stars. The dissipative effects of electron viscosity and mutual friction resulting from electron-vortex scattering are also included. It is shown that Alfvén waves are replaced by cyclotron-vortex waves that have not been previously derived from MHD theory. The cyclotron-vortex waves are analogous to Alfvén waves with the tension arising from the magnetic energy density replaced by the vortex energy density. The equations are then put into a simplified form useful for studying the effect of the interior magnetic field on the dynamics. Of particular interest is the crust–core coupling time, which can be inferred from pulsar glitch observations. The hypothesis that cyclotron-vortex waves play a significant role in the core spin-up during a glitch is used to place limits on the interior magnetic field. The results are compared with those of other studies.     

Nonlinearly coupled electromagnetic ion-cyclotron and magnetosonic waves in astrophysical plasmas

A set of three nonlinearly coupled equations governing the interaction between electromagnetic ion-cyclotron and magnetosonic waves is derived. In appropriate limiting cases, the set yields simplified equations. On the other hand, the full set of equations is used to derive a general dispersion relation for the parametric interaction of electromagnetically modulated ion-cyclotron wave packets. An analytical expression for the growth rate of the electromagnetic modulational instability is presented. The relevance of our investigation to non-thermal electromagnetic fluctuations in astrophysical and cometary plasmas is pointed out.     

Bifurcations of dust acoustic solitary waves and periodic waves in an unmagnetized plasma with nonextensive ions

Bifurcations of dust acoustic solitary waves and periodic waves in an unmagnetized plasma with q-nonextensive velocity distributed ions are studied through non-perturbative approach. Basic equations are reduced to an ordinary differential equation involving electrostatic potential. After that by applying the bifurcation theory of planar dynamical systems to this equation, we have proved the existence of solitary wave solutions and periodic wave solutions. Two exact solutions of the above waves are derived depending on the parameters. From the solitary wave solution and periodic wave solution, the effect of the parameter (q) is studied on characteristics of dust acoustic solitary waves and periodic waves. The parameter (q) significantly influence the characteristics of dust acoustic solitary and periodic structures.     

Ion acoustic solitary and shock waves with nonextensive electrons and thermal positrons in nonplanar geometry

The nonlinear wave structures of ion acoustic waves (IAWs) in an unmagnetized plasma consisting of nonextensive electrons and thermal positrons are studied in bounded nonplanar geometry. Using reductive perturbation technique we have derived cylindrical and spherical Korteweg-de Vries-Burgers’ (KdVB) equations for IAWs. The presence of nonextensive q-distributed electrons is shown to influence the solitary and shock waves. Furthermore, in the existence of ion kinematic viscosity, the shock wave structure appears. Also, the effects of nonextensivity of electrons, ion kinematic viscosities, positron concentration on the properties of ion acoustic shock waves (IASWs) are discussed in nonplanar geometry. It is found that both compressive and rarefactive type solitons or shock waves are obtained depending on the plasma parameter.     

Stellar wind models with Alfvén waves

It is known that stellar winds from late type stars are of mixed thermal and magnetic origin. The stellar wind model presented in this work uses the hydrodynamic equations of mass and momentum conservation and closes the system of equations with a detailed energy equation. Both momentum and energy equations have terms due to the effects of Alfvén waves. A smooth transition between the two regimes for Alfvén wave propagation, the undamped and the damped modes, is achieved by considering the geometrical mean of both wave amplitudes. It will be shown that the initial push on the plasma is provided by the mechanical heating input, and that further out the Alfvén waves take over energetically.     

On the head-on collision between two ion acoustic solitary waves in a weakly relativistic plasma containing nonextensive electrons and positrons

The head-on collision of two ion acoustic solitary waves propagating in opposite directions in a weakly relativistic electron-positron-ion plasma composed of weakly relativistic warm ion fluid and nonextensive electrons, positrons is investigated. Using extended Poincaré-Lighthill-Kuo method, the Korteweg-de Vries equations and the analytical phase shifts after the head-on collision of two solitary waves are derived. The effects of the nonextensive parameter, positron-to-electron density ratio, ion-to-electron temperature ratio, electron-to-positron temperature ratio and relativistic factor on the phase shifts are studied. It is found that these parameters can significantly influence the phase shifts of solitary waves.     

Equatorially trapped Rossby waves in radiative stars

Observations by recent space missions reported the detection of Rossby waves (r-modes) in light curves of many stars (mostly A, B, and F spectral types) with outer radiative envelope. This article aims to study the theoretical dynamics of Rossby-type waves in such stars. Hydrodynamic equations in a rotating frame were split into horizontal and vertical parts connected by a separation constant (or an equivalent depth). Vertical equations were solved analytically for a linear temperature profile and the equivalent depth was derived through free surface boundary condition. It is found that the vertical modes are concentrated in the near-surface layer with a thickness of several tens of surface density scale height. Then with the equivalent width, horizontal structure equations were solved, and the corresponding dispersion relation for Rossby, Rossby-gravity, and inertia-gravity waves was obtained. The solutions were found to be confined around the equator, leading to the equatorially trapped waves. It was shown that the wave frequency depends on the vertical temperature gradient as well as on stellar rotation. Therefore, observations of wave frequency in light curves of stars with known parameters (radius, surface gravity, rotation period) could be used to estimate the temperature gradient in stellar outer layers. Consequently, the Rossby mode may be considered as an additional tool in asteroseismology apart from acoustic and gravity modes.     

Arbitrary amplitude ion-acoustic solitary waves in superthermal electron-positron-ion magnetoplasma

Arbitrary amplitude ion-acoustic solitary waves propagating in a magnetized plasma composed of positive ions, superthermal electrons and positrons are investigated. For this purpose, the ions are represented by the hydrodynamical fluid equations while the non-Maxwellian electrons and positrons densities are assumed to follow kappa (κ) distribution. The basic equations are reduced to a pseudoenergy-balance equation. Existence conditions for large amplitude solitary waves are presented. The analytical and numerical analysis of the latter show that the ion-acoustic solitary wave can propagate only in the subsonic region in our plasma system and it is significantly influenced by the plasma parameters. The present analysis could be helpful for understanding the nonlinear ion-acoustic solitary waves propagating in interstellar medium and pulsar wind, which contain an excess of superthermal particles.     

The numerical calculation of wave-fields for gravity waves propagating in an inhomogeneous atmosphere

Numerical solutions of the hydrodynamic equations are used to examine the wave-fields for gravity waves propagating upwards in a horizontally stratified inhomogeneous atmosphere. Calculations using a multilayer approach and also using a new direct integration method have been performed. These have shown that a pronounced reflection of the waves in the lower mesosphere is possible.