Transversal small-scale perturbations in arbitrary three-dimensional (3-D) spatially non-uniform space plasma systems with magnetic surfaces are analysed. A system of equations describing the disturbances is deduced. It is shown that in dipole geometry of magnetic field the disturbances of two different polarizations can be realized. In the framework of dipole geometry equations for MHD-eigenmodes are obtained and stability of the disturbances is investigated.