Alfvenic fluctuations as asymptotic states of MHD turbulence

Satellite observations of the solar wind show a fully developed turbulent state in which the velocity and magnetic fluctuations are often very strongly correlated. To investigate a possible dynamical origin of this correlation, a two-point closure method is applied to study the time evolution of incompressible, homogeneous, mirror-symmetric MHD turbulence with nonzero velocity-magnetic fields correlation. Analytical and numerical evidence is presented showing that nonlinear interactions lead asymptotically to a state of maximal correlation. This supports a recent conjecture, based on one-point closure of Dobrowolny, Mangeney and Veltri (1980). Implications of this result for the origin of strongly correlated turbulence in the solar wind are discussed.