Alignment of Velocity and Magnetic Fluctuations in Anisotropic MHD Turbulence

There has been recent theoretical interest in the effect of the alignment of velocity and magnetic fluctuations in three-dimensional (3D) MHD turbulence with a large-scale magnetic field [Boldyrev 2005, 2006]. This theory predicts that the angle $\theta$ between the velocity and magnetic fluctuation vectors has a scaling of $\theta \propto \lambda^{1/4}$, where $\lambda$ is the spatial scale of the fluctuations. There have also been simulations on 3D forced MHD turbulence that supports this prediction [Mason {\em et al.} 2006, 2007]. Based on decaying two-dimensional (2D) turbulence, we have found the scaling of $\theta \propto \lambda^{1/4}$ within a range of time interval and spatial scales, despite the fact that Boldyrev's phenomenological theory relies on physical mechanisms operative in fully 3D turbulence in the presence of a strong external field. Higher resolution simulations and scaling analysis, based on pseudo-Alfven waves in 2D, will be presented.