Wave propagation is studied in a sufficiently anisotropic random medium that
backscattering along one direction can be neglected. A Fokker-Planck equation
is derived the solution to which would provide a complete statistical
description of such directed waves. The Fokker-Planck equation is mapped onto
an su(1,1) ferromagnet and its symmetries are identified. Using the symmetries
asymptotic wave function distributions are computed and used to show that
directed wave functions fill space uniformly and do not have multifractal
character.Comment: 5 pages. Submitted to Phys Rev Let