Speaker
Daniela Grasso
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1071.pdf
Lagrangian Coherent Structures in magnetized plasmas: Particle
transport in a time dependent magnetic configuration
D. Grasso1 , G. Di Giannatale2 , M.V. Falessi3 , F. Pegoraro4 ,T.J. Schep5
1 ISC - CNR and Politecnico di Torino, Dip. Energia C.so Duca degli Abruzzi 24, Torino. Italy
2 IGI - CNR, Corso Stati Uniti 4, Padova, Italy
3 ENEA, C. R. Frascati, Via E. Fermi 45, Frascati, Italy
4 Dip. Fisica E. Fermi, Pisa University, largo Pontecorvo 3, Pisa, Italy
5 Dep. Applied Physics, Eindhoven Univ. of Technology, 5600MB Eindhoven, The Netherlands
The understanding of transport phenomena in low-collisionality, magnetized plasmas is one of
the most challenging tasks in the investigation of both laboratory and space plasmas due to
their generally non-diffusive nature. In recent years the concept of Lagrangian Coherent Struc-
tures (LCS) has been introduced by G. Haller in the context of transport processes in complex
fluid flows [1]. LCS are a generalization of the dynamical structures observed in autonomous
and periodic systems to temporally aperiodic flows. Therefore, they separate the flow domain
into macro-regions inside which fast mixing phenomena take place. Over the finite time span
which characterizes the LCS these macro-regions do not exchange fluid elements and thus act
as transport barriers. In two recent works [2, 3] we apply this conceptual framework to the
study of particle transport in a magnetized plasma. Futhermore we introduce a simplified model
that allows us to consider explicitly a magnetic configuration evolving in time on timescales
comparable to the particle transit time through the configuration. This analysis requires that a
system that is aperiodic in time is investigated. In this case the Poincaré map technique can-
not be applied and LCSs remain the only viable tool. By means of a numerical procedure we
investigate the LCSs in the case of a magnetic configuration with two island chains that are gen-
erated by magnetic reconnection and evolve nonlinearly in time. The comparison with previous
results [4, 5], obtained by assuming a fixed magnetic field configuration, allows us to explore
the dependence of transport barriers on the particle velocity.
References
[1] G Haller. Annual Review of Fluid Mechanics, 47:137–162, 2015.
[2] G Di Giannatale, MV Falessi, D Grasso, F Pegoraro, and TJ Schep. submitted to Physics of Plasmas.
[3] G Di Giannatale, MV Falessi, D Grasso, F Pegoraro, and TJ Schep. submitted to Physics of Plasmas.
[4] G Rubino, D Borgogno, M Veranda, D Bonfiglio, S Cappello, and D Grasso. submitted to Plasma Physics and
Controlled Fusion, 57(8):085004, 2015.
[5] MV Falessi, F Pegoraro, and TJ Schep. Journal of Plasma Physics, 81(05):495810505, 2015.
