The collective kinetic interaction of a neutrino distribution with electrostatic waves propagating in a dense plasma is considered. A Klimontovich-type kinetic equation for the neutrino gas in a plasma is derived, and the resulting kinetic description is applied to study the processes of the neutrino Landau damping and the neutrino-beam–plasma instability.

Relativistic and non-relativistic particle acceleration along and across a magnetic field, and the generation of an electric field transverse to the magnetic field, both induced by almost perpendicularly propagating electrostatic waves in a relativistic magnetized plasma, are investigated theoretically on the basis of relativistic quasilinear transport equations. The electrostatic waves accelerate particles via Landau or cyclotron damping, and the ratio of parallel and perpendicular drift velocities vs||/vd can be proved to be proportional to k||/k⊥. Simultaneously, an intense cross-field electric field E0 = B0 × vd/c is generated via the dynamo effect owing to perpendicular particle drift to satisfy the generalized Ohm's law, which means that this cross-field particle drift is identical to E × B drift. The relativistic quasilinear transport equations for relativistic cross-field particle acceleration are derived by Lorentz transformation of the relativistic quasilinear momentum-space diffusion equation in the moving frame of reference without the electric field and the cross-field particle drift. They can be applied to the investigation of the relativistic perpendicular particle acceleration that may possibly occur in space plasmas.

Generalized dispersion relations for Alfvén waves are derived, accounting for arbitrary values of ω/ωci, k⊥ρi, and k⊥λe, where ω(ωci) is the wave (ion gyro) frequency, k⊥ = 2π/λ⊥ the perpendicular (to the external magnetic field line) wavenumber, and ρi(λe) the ion gyroradius (electron skin depth). Our dispersion relations are appropriate for deducing the relationships of the dispersive (inertial and kinetic) Alfvén waves with other plasma modes. The present results can be considered as a prerequisite for understanding some salient features of the broadband electromagnetic/electrostatic waves that are frequently observed by the Freja and FAST spacecraft in the auroral zone of the Earth's ionosphere.

This paper reports the results of computations to obtain the spatial distributions of the charged particles in a bounded active plasma dominated by negative ions. Using the fluid model with a constant collision frequency for electrons, positive ions and negative ions the cases of both detachment-dominated gases (such as oxygen) and recombination-dominated gases (such as chlorine) are examined. It is concluded that it is valid to use a Boltzmann relation ne = ne0exp(eV/kT) for the electrons of density ne, where the temperature T is approximately the electron temperature Te, and that the density nn of the negative ions at low pressures obeys nn = nn0exp(eV/kTn), where Tn is the negative-ion temperature. However, at high pressure in detachment-dominated gases where the ratio of negative-ion density to electron density is constant and greater than unity, and when the attachment rate is larger than the ionization rate, the negative ions are distributed with the same effective temperature as the electrons. In all other cases there is no simple relationship. Thus to put nn/ne = const, nn = ne0exp(eV/kTe) and nn = nn0exp(eV/kTn) simultaneously is mathematically inconsistent and physically unsound. Accordingly, expressions deduced for ambipolar diffusion coefficients based on these assumptions have no validity. The correct expressions for the situation where nn/ne = const are obtained without invoking a Boltzmann relation for the negative ions.

A class of Hamiltonian models is considered that both includes many important examples from fluid and plasma theory and admits an elementary and simple abstract formulation. The formalism is illustrated by explicit expressions for both incompressible and compressible ideal magnetohydrodynamics, including a Coriolis force term and, in the incompressible case, allowing for a sharp ideally conducting boundary. The small-amplitude expansion is studied for a general background state, and the abstract setting gives much control of the usually messy algebra. One result is a new general and surprisingly simple symmetric expression for the coupling strength in the resonant three-wave interaction process. It may provide a convenient starting point for wave coupling calculations and seems suitable for the use in conjunction with computer algebra when various concrete models are considered.

The issue of dynamical anisotropy in helical three-dimensional magnetohydrodynamic turbulence with a mean magnetic field B0 is investigated. Using high-resolution direct numerical simulations, we follow the evolution of various isotropic initial states characterized by their different values of the kinetic helicity. The cross helicity and magnetic helicity of the initial conditions are also varied. In agreement with earlier work, we find that such initial states become anisotropic in of order an eddy-turnover time, with correlation lengths parallel to B0 remaining largely unchanged while finer scales are excited in the perpendicular directions. Moreover, it is found that the development of both the anisotropy and the energy are essentially independent of the initial level of kinetic helicity. The physics associated with this latter feature is discussed.

The MHD analogue of the Brunt/Väisälä frequency, NB, in a magnetized, ideally conducting plasma is obtained, with the vertical component of the magnetic field, Br, taken into account. The magnetic field vector (Br, Bθ, Bϕ) is assumed to satisfy the condition B·∇B ≈ BrdB/dr, which holds in many cases of interest. The frequency NB happens to depend, generally speaking, on the magnetic field orientation relative to the direction of gravity. However, for an isentropic gas, the convective instability criterion is governed by the magnetic field strength (rather than by the orientation of B). In general, the magnetic field has a stabilizing (destabilizing) effect if B/ρ grows (decreases) along the vertical axis r. This conclusion seems not to depend on the specific magnetic field configuration.