Transversal small-scale MHD perturbations in space plasma with magnetic surfaces

This paper analyzes transversal small-scale perturbations in arbitrary three-dimensional (3D) spatially nonuniform space plasma systems with magnetic surfaces and deduces a system of equations for these perturbations. It shows that a dipole magnetic field can have perturbations of two different polarizations. Within dipole geometry, it derives equations for MHD-eigenmodes and investigates stability of the perturbations.