Can we understand Alfvénic turbulence via simulations of the MHD equations?

Solar Wind 8, AIP Conf. Proc. 382, p.250, 1996

R. Grappin and A. Mangeney

Abstract

Solar wind turbulence in the range between one day and several minutes may be looked at in different ways: on the one side MHD turbulence in a mean magnetic field, on the other almost freely propagating waves, with wave fronts being distorted by the streams and large-scale transverse magnetic gradients, and stretched by the mean diverging flow. We review some of the relevant numerical work and phenomenology. In particular, we propose a phenomenology of homogeneous MHD turbulence with a mean magnetic field (based on Iroshnikov-Kraichnan's ideas) in which the spectrum exhibits some anisotropy, not in the spectral index, but in the inertial range extent. In the solar wind, the situation is far from this highly idealized one; one of the main problems is that of the competition between the symmetries around two different axis: mean field and radial direction.