Structure of Alfvén waves at the skin-depth scale

This analytical study demonstrates that shear Alfvén waves having transverse scale on the order of the electron skin depth exhibit a collisionless divergence determined by propagation cones that emanate from the edges of the exciting structures. Axial current channels are found to spread radially due to the skin effect up to the cone trajectories and at distances of a few wavelengths from the exciter develop radial diffraction patterns. For values of the collision frequency slightly larger than the wave frequency resistive diffusion allows the axial currents to expand beyond the cone trajectories.