Dr. Matteo Falessi （ENEA Frascati research center, Italy）
Time：Thursday (Nov. 9th) afternoon, at 2:00pm.
Title: Transport processes in plasma physics: a new approach
Venue: Rm. 413, Bld. 11#, Yuquan Campus
Abstract: A dynamical system framework is used to describe transport of passive tracers in plasmas. For periodic systems with one degree of freedom the Poincare map provides a splitting of the (phase-)space into regions where tracers have different kinds of motion: periodic, quasi-periodic or chaotic. The boundaries of these regions are transport barriers; i.e., a trajectory cannot cross such boundaries during the whole evolution of the system. Lagrangian Coherent Structure (LCS) generalize this method to systems with the most general time dependence, splitting the (phase-)space into regions with different qualitative behaviours. This leads to the definition of finite-time transport barriers, i.e. trajectories cannot cross the barrier for a finite amount of time. This methodology can be used to identify fast recirculating regions in the dynamical system and to characterize the transport between them and, therefore, as post-processing diagnostic in MHD, kinetic or hybrid simulations.