  Interaction of impulsively generated MHD waves with a one-dimensional plasma
inhomogeneity, transverse to the magnetic field, is considered in the
three-dimensional regime. Because of the transverse inhomogeneity, MHD
fluctuations, even if they do not include initially any density perturbation,
evolve toward states where the compressible components tend to become
predominant. The propagating MHD pulse asymptotically reaches a quasi-steady
state with the final levels of density perturbation weakly depending on the
degree of non-planeness of the pulse in the homogeneous transverse direction
and somewhat stronger depending on plasma beta. Our study demonstrates the
necessity of incorporation of compressible and 3D effects in theory of Alfven
wave phase mixing. However, as far as the dynamics of weakly non-plane Alfven
waves is concerned it can still be qualitatively understood in terms of the
previous 2.5D models.
