Intermittency in fluid and MHD turbulence analyzed through the prism of moment scaling predictions of multifractal models

Abstract. In the presence of waves due e.g. to gravity, rotation or a quasi-uniform magnetic field, energy transfer time-scales, spectra and physical structures within turbulent flows differ from the fully developed fluid case, but some features remain such as intermittency or quasi-parabolic behaviors of normalized moments of relevant fields. After reviewing some of the roles intermittency can play in various geophysical flows, we present results of direct numerical simulations at moderate resolution and run for long times. We show that the power-law scaling relations between kurtosis K and skewness S found in multiple and diverse environments can be recovered using existing multifractal intermittency frameworks. In the specific context of the She-Lévêque model (1994) generalized to MHD and developed as a two-parameter system in Politano and Pouquet (1995), we find that a parabolic K (S) law can be recovered for maximal intermittency involving the most extreme dissipative structures.