Thursday 26 Feb 2015: Seminar: Non-asymptotic and non-universal turbulence in magnetic fields (THU 11am)
Prof Wolf-Christian Mueller - Technical University, Berlin
Physics, 4th floor 11:00-12:00
Magnetohydrodynamic (MHD) turbulence in a mean magnetic field can exist in fundamentally different regimes. Its character can, for example, be changed from "weak" to "strong" where these attributes basically express different ratios of characteristic timescales of turbulent dynamics. This possibility of manipulation can be exploited by carefully changing the large-scale excitation mechanism of the turbulence. A regime of "weakened" MHD turbulence is presented that exhibits isotropic similarity properties which are beyond the current theoretical understanding of turbulence in magnetic fields and whose dynamics are explained in terms of quasi-resonant nonlinear interactions. This new flavour of MHD turbulence bridges the gap that exists between the asymptotic weak turbulence theory and critically balanced Goldreich-Sridhar phenomenology. It is of particular interest for the solar wind where turbulence with different similarity properties is found under varying large-scale conditions.