Anisotropy in incompressible and compressible 3D MHD turbulence.

Using direct numerical simulation results we discuss how the presence of a dc magnetic field (B0) in initially isotropic turbulent magnetohydrodynamic (MHD) flows leads to anisotropy in the small-scale velocity and magnetic fields. In such cases, the small-scale vorticity and current structures tend to elongate and align with B0. The incompressible behaviour is also compared to weakly compressible results (sonic Mach number <0.5). The simulations indicate that while density and longitudinal pressure fluctuations remain isotropic for the compressible systems, the v and b fluctuations behave quite similarly to their incompressible counterparts, exhibiting substantial anisotropies even at the modest Reynolds numbers employed here. [ABSTRACT FROM AUTHOR]