Jena 2013 – wissenschaftliches Programm

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SYPA: Symposium Plasma-Astrophysik

SYPA 1: Plasma-Astrophysics

SYPA 1.1: Hauptvortrag

Dienstag, 26. Februar 2013, 16:30–17:00, HS 2

Magnetic Reconnection and Stochastic Plasmoid Chains in High-Lundquist-number Plasmas — •Nuno Loureiro — Instituto de Plasmas e Fusão Nuclear, IST, Lisbon, Portugal

Over the last few years, the theoretical understanding of magnetic reconnection in large-scale fluid systems has undergone a major paradigm shift. The steady-state model of reconnection described by the famous Sweet-Parker (SP) theory, which dominated the field for ∼ 50 years, has been replaced with an essentially time-dependent, bursty picture of the reconnection layer, dominated by the continuous formation and ejection of multiple plasmoids. Whereas in the SP model reconnection was predicted to be slow, a major implication of this new paradigm is that reconnection in fluid systems is fast, i.e., independent of the Lundquist number of the system (S=L V_A/η, where L is the system size, V_A the Alfvén velocity and η the resistivity), provided that the system is large enough.

In this talk, I will review the recent developments in reconnection that led to this essentially new framework. Both the linear theory describing the instability of current layers to plasmoid formation (including a new development which suggests that current sheets may also be unstable to the Kelvin-Helmholtz instability) and a nonlinear, statistical theory describing the dynamics of a stochastic plasmoid chain will be analyzed. I will discuss results from direct numerical simulations that both confirm and extend the theory, with particular emphasis on the plasmoid size and width distribution functions. New results extending the above investigations to fully 3D systems will be presented.