Yi-Min Huang, Princeton University

Title: New Perspectives on Magnetic Reconnection — From Plasmoid Instability to Self-Generated Turbulence  (Video)

Abstract:  Magnetic reconnection is a fundamental physical process that allows magnetic field lines to break the frozen-in constraint of ideal magnetohydrodynamics (MHD), changing magnetic topology while at the same time converting stored magnetic energy into plasma energy. It is generally believed to be the underlying mechanism that powers energetic events over a wide range of scales, including sawtooth crashes in magnetic fusion devices, magnetospheric substorms, solar flares, and coronal mass ejections. In recent years, theoretical analysis and numerical simulations provide strong evidence that large-scale, high-Lundquist-number magnetic reconnection is susceptible to the plasmoid instability and becomes sporadic, therefore the traditional picture of two-dimensional laminar reconnection needs a major revision. In this talk, I will give an overview of recent progress in the roles of plasmoid instability on magnetic reconnection. I will first discuss the linear tearing instability in a reconnecting current sheet that eventually leads to a disruption of the current sheet and triggers onset of fast reconnection. Then I will discuss various scenarios of plasmoid-mediated reconnection in fully nonlinear regimes, with resistive and Hall MHD simulations. Finally, I will discuss results from a recent 3D simulation, where plasmoid instability is shown to facilitate self-generated turbulent reconnection.