Speaker
Description
Plasma turbulence is a widespread phenomenon that is important in many astrophysical systems. It can be described as the superposition of Alfvén wave packets on various scales in space and time, which interact with each other non-linearly, giving rise to the direct energy cascade in 3D incompressible MHD turbulence. We study the temporal and spatial properties of the energy transfer process by computing the spatio-temporal correlation between fluctuations of the Elsässer fields. To this end, direct numerical simulations are performed, in which the fluctuations are measured in the directions parallel and perpendicular to the local magnetic field. This is done in the co-moving Quasi-Lagrangian reference frame to minimize the large-scale sweeping effect.
The single-time correlation between parallel and perpendicular fluctuations allows the measurement of spatial properties such as the elongation of the turbulent structures. The multi-time correlation, on the other hand, gives insight into the time scales involved in the cross-scale energy transfer and the propagation of Alfvén waves. First results for both are presented and compared to predictions made by phenomenological models of MHD turbulence.
