MPS Seminar: Plasma Instabilities in Magnetic Reconnection, Formation of Plasmoids and Supra-Arcade Downflows (Y.-M. Huang)

Inrecent years, theoretical analysis and numerical simulations indicate thatlarge-scale, high Lundquist number magnetic reconnection is susceptible toplasma instabilities and becomes sporadic and even turbulent, therefore thetraditional picture of two-dimensional laminar reconnection needs a majorrevision. In this talk I will discuss two types of instabilities: the plasmoidinstability in the reconnection layer and the Rayleigh-Taylor type instabilityin the exhaust region. I will first review key results from previous work on 2Dplasmoid instability in both linear and nonlinear regimes, including the rolesof the plasmoid instability in enabling fast reconnection in resistive MHD, aswell as in triggering even faster Hall reconnection. Then I will present morerecent results on turbulent reconnection induced by 3D plasmoid instabilities.Finally, I will talk about Rayleigh-Taylor type instability in the exhaustregion of reconnection, which is proposed as a candidate for the mechanism ofsupra-arcade downflows usually observed above post-eruption coronal arcades.