A modified electron whistler dispersion law is derived in the cold-plasma approximation for analytical treatment and simplified numerical calculations of wave propagation in a wide range of ratios ωc/ωp of electron gyro- to plasma frequencies if the wave frequency is much less than ωp. The net contribution of ions to the wave dispersion law is expressed through the value of the lower-hybrid resonance frequency ωlhr only. This approximate dispersion law is valid in a wide frequency domain, that is, from the range of ωlhr until the domain where the contribution of ions can be neglected. A comparison of geometrical-optics ray trajectories calculated by the use of modified and total cold-plasma electron whistler dispersion laws is presented for the case of the Earth's plasma environment. Computer simulations of dynamical spectra of whistler waves excited by lightning discharges and registered in remote regions of the Earth's plasmasphere reveal good numerical stability of the developed ray-tracing code.

In most studies, the properties of dust-acoustic solitons are derived from the first integral of the Poisson equation, in which the shape of the pseudopotential determines both the conditions in which a soliton may exist and its amplitude. Here this first integral is interpreted as conservation of total momentum, which, along with the Bernoulli-like energy equations for each species, may be cast as the structure equation for the dust (or heavy-ion) speed in the wave. In this fluid-dynamic picture, the significance of the sonic points of each species becomes apparent. In the wave, the heavy-ion (or dust) flow speed is supersonic (relative to its sound speed), whereas the protons and electrons are subsonic (relative to their sound speeds), and the dust flow is driven towards its sonic point. It is this last feature that limits the strength (amplitude) of the wave, since the equilibrium point (the centre of the wave) must be reached before the dust speed becomes sonic. The wave is characterized by a compression in the heavies and a compression (rarefaction) in the electrons and a rarefaction (compression) in the protons if the heavies have positive (negative) charge, and the corresponding potential is a hump (dip). These features are elucidated by an exact analytical soliton, in a special case, which provides the fully nonlinear counterpoint to the weakly nonlinear sech2-type solitons associated with the Korteweg–de Vries equation, and indicates the parameter regimes in which solitons may exist.

The distribution of plasma and electric fields close to the far side of the Moon are discussed. The existence of a strong double layer behind the Moon is predicted and its parameters are investigated. Electric currents associated with this double layer and finite conductivity inside the Moon are estimated. The fluxes of suprathermal electrons behind the Moon in different energy ranges are calculated and compared with the experimental data. It is shown that the theoretical results are in qualitative agreement with the data obtained by Lunar Prospector and the Apollo 15 subsatellite.

The nonlinear interaction between large-amplitude electromagnetic waves and electron-acoustic (EA) waves in a two-electron-temperature plasma is considered, taking into account the combined effects of the radiation pressure and the thermal force involving the differential Joule heating of the electrons caused by the electromagnetic waves. By employing a fluid approach, we derive a system of coupled equations for the electromagnetic waves and the EA waves; the latter are nonlinearly driven by the radiation and thermal forces. We have carried out a normal mode analysis of our nonlinearly coupled equations, and have derived a general dispersion relation that is useful for studying different types of parametric instabilities. A new class of modulational instability in the collision-dominated regime is identified. The implications for space and laboratory plasmas are pointed out.

The method of matched asymptotic approximations is used to examine an ordering of the physical quantities in a collisional plasma–collisional sheath model that has not been previously explored, namely in the constant ion mean free path model with high electric field. The asymptotic theory for a collision-dominated space-charge sheath at a negative surface is developed for the case when the ions interact with neutral particles as rigid spheres while the electric field is high both in the sheath and in the quasineutral plasma. The ion mobility is inversely proportional to the square root of the electric field in such a case. The ratio λD/L of the Debye length at the center of the quasineutral plasma to a characteristic dimension of the plasma is considered as a small asymptotic parameter. The general structure of the asymptotic solution obtained is similar to that in the case of low electric field (or in the framework of the model of constant collision frequency), considered by previous workers; however, the scalings are different. In particular, the thickness of the sheath is found to have the order λ4/5DL1/5, while the respective order in the case of low electric field is λ2/3DL1/3.

Inelastic Compton scattering of photons by hydrogenic ions in a classical nonideal plasma is investigated. An effective pseudopotential model taking into account plasma screening and collective effects is applied to describe the interaction potential in a nonideal plasma. The screened atomic wave functions and energy eigenvalues for the ground and excited states of the hydrogenic ion in a classical nonideal plasma obtained by the Ritz variational and perturbational methods. The expression for the lowest-order transition matrix element is obtained by a two-photon process associated with terms quadratic in the vector potential A. The inelastic Compton scattering cross-section horn the 1s ground state to the 2p excited state is obtained as a function of the incident photon energy, Debye length, and the non-ideality plasma parameter. It is found that the collective effect reduces the cross-section. The collective effect on the cross-section is decreased with increasing Debye length.

Orientation phenomena for direct 1s → 2p±1 excitations in electron–hydrogenic-ion collisions are investigated in a classical nonideal plasma. An effective pseudopotential model taking into account plasma-screening and collective effects is applied to describe the interaction potential in a nonideal plasma. The orientation parameter for direct 1s → 2p±1 excitations in a nonideal plasma is obtained as a function of the impact parameter, the nonideal-plasma parameter, the Debye length, and the projectile energy. The result shows that the nonideal effect reduces the propensity of the 1s → 2p−1 transition. It is also found that the nonideal effect on the orientation parameter increases with increasing projectile energy.

The classical electron–ion Coulomb bremsstrahlung process is investigated in a nonideal plasma. An effective pseudopotential model taking into account plasma-screening and collective effects is applied to describe the electron-ion interaction potential in a nonideal plasma. The screened hyperbolic-orbit trajectory method is applied to the motion of the projectile electron in order to investigate the bremsstrahlung radiation cross-section as a function of the scaled impact parameter, eccentricity, nonideal-plasma parameter, Debye length, projectile energy, and photon energy. It is found that the collective effect reduces the bremsstrahlung radiation cross-section on both the soft- and hard-photon cases. For small impact parameters, the nonideal-plasma effect on the bremsstrahlung radiation cross-section is found to be quite small. It is also found that the maximum position of the bremsstrahlung radiation cross-section gets closer to the target ion with increasing nonideal-plasma effect.

An exact Sagdeev equation for arbitrary-amplitude solitary kinetic Alfvén waves in a non-thermal plasma is derived. For small β′, the proportion of fast electrons, an analytical expression for the exact pseudopotential V (φ) is obtained. For several values of β′, the Sagdeev potential V (φ) has been calculated by integrating the Sagdeev equation. It is found that, depending on the values of β′, both hump and dip solitons exist.

Numerical calculations are performed based on a set of equations that describe the non-steady, nonlinear interactions between a moving body in space and plasma. The results show that density cavitons and potential solitons are formed owing to modulational instability if the envelope of the high-frequency modulational field is sufficiently intense.

This paper considers single-particle trajectories in a planar sheared force-free magnetic field. A specific feature of this magnetic configuration is the absence of both gradient and curvature magnetic drifts, as well as a diamagnetic force along field lines. Therefore, in the framework of the drift approximation, the motion of the particle guiding centre does not feel the magnetic field's non-uniformity. Here we discuss how the latter affects actual particle trajectories, making them quite different from simple circular gyromotion even when the Larmor radius is small. It is also shown how magnetic confinement ceases to work when the Larmor radius becomes comparable to the spatial scale of the field variation.