Title : Magnetic Reconnection in a Weakly Ionized Plasma Speaker Name: Prof. Vyacheslav (Slava) Lukin Speaker Institution : NSF/U. Washington Abstract : Magnetic reconnection, the prototypical example of a nonlinear magnetized plasma phenomenon that can couple physical processes across decades of spatial and temporal scales, is known or conjectured to take place in a variety of laboratory settings, throughout the heliosphere, as well as in any number of astrophysical systems. There is active ongoing experimental, computational, and theoretical research into the basic physics of magnetic reconnection in a variety of plasma parameter regimes, from classical fully ionized plasmas, to relativistic radiation-dominated plasmas, to strongly-coupled high energy density plasmas. In this talk, I will present results of the first self-consistent multi-fluid simulations of magnetic reconnection in a reacting partially ionized plasma, where the ionized and neutral fluids are treated as coupled but distinct. Different plasma processes, such as ionization and recombination, ion-neutral interaction via charge-exchange collisions, Hall currents, and radiative losses can become the dominant factors in determining the reconnection rate and the structure of the reconnection region in different parameter regimes. The HiFi multi-fluid modeling framework has been used to implement the above processes in a single self-consistent model and to perform 2D simulations of magnetic reconnection under a variety of plasma conditions. Simulation results addressing the rate of magnetic reconnection, the structure of a reconnection region in a weakly ionized plasma, and the possible implications for magnetic reconnection in the partially ionized solar chromosphere will be presented.