Abstract

Magnetised plasma turbulence pervades the Universe and is believed to play an important role in a variety of astrophysical processes, ranging from heating in the solar corona to the transport of angular momentum in accretion discs. Unfortunately, despite its wide ranging applicability, the subject still lacks a firm theoretical foundation, even in the simplest case of incompressible, field-guided MHD turbulence.

Significant advances in computational power over the last decade have led to numerical simulations becoming an extremely valuable resource. The numerical results are used to test competing theoretical models and to guide future progress. Indeed, the results of some recent high-resolution simulations of driven incompressible MHD turbulence in the presence of a strong background magnetic field have highlighted a number of deficiencies in our understanding. Motivated by the numerical results, in 2006 Boldyrev (Phys. Rev. Lett. 96, 115002) introduced a new phenomenological model of the energy cascade. The key prediction is a process known as `scale-dependent dynamic alignment’, wherein the velocity and magnetic field fluctuations tend to align within a small scale-dependent angle in the field-perpendicular plane. In this talk I will introduce the theory and describe a series of high-resolution numerical simulations that have been specially designed in order to test the new theoretical predictions.