Drift-Alfvén vortices with finite ion gyroradius and electron inertia effects

Abstract

A two-fluid plasma model is used to analyze drift-Alfvén vortices in a magnetized, inhomogeneous, warm plasma. This low-β model retains the effects of finite electron mass and of finite ion gyroradii. The vortices are described by two potentials: the electrostatic potential and one component of the vector potential. The background plasma is assumed to have locally a linear density profile. Solutions in the form of dipoles, which propagate with constant velocity across a strong, uniform magnetic field, are analyzed. A general dispersion relation between the eigenvalues inside and outside the separatrix is derived. The analysis of this dispersion relation and of the spatial vortex structure leads to a general classification of two-potential vortices. Explicit solutions are presented for dipole vortices in the limit of zero electron inertia where finite gyroradius effects are retained and in the limit of cold ions where finite electron mass is taken into account.