  In this paper we systematically study the spectrum and structure of
incompressible MHD turbulence by means of high resolution direct numerical
simulations. We considered both balanced and imbalanced (cross-helical) cases
and simulated sub-Alfvenic as well as trans-Alfvenic turbulence. This paper
extends numerics preliminarily reported in Beresnyak & Lazarian (2008). We
confirm that driven imbalanced turbulence has a stationary state even for high
degrees of imbalance. Our major finding is that the structure of the dominant
and subdominant Alfvenic components are notably different. Using the most
robust observed quantities, such as the energy ratio, we were able to reject
several existing models of strong imbalanced turbulence.
