GEM: Anti-Parallel and Component Merging Scenarios in Collisionless Reconnection

University Of California-San Diego, La Jolla CA

Investigators

Abstract

Recent work has led to a number of surprising results that challenge many of the conventional viewpoints regarding the essential physics of magnetic reconnection. This project will re-examine the physics of reconnection utilizing a Particle-In-Cell plasma simulation code. An important aspect of the simulations is that they will be run using an open boundary model rather than the traditional periodic boundary condition. The initial results from this approach appear quite promising since the artificial recirculation that is inherent with periodic boundary conditions is completely eliminated. Plasma and magnetic flux is allowed to enter and exit the system as needed. The resulting simulations effectively mimic a much larger system than is possible with periodic boundary conditions. These simulations have led to a new understanding of the structure of the electron diffusion region and its effect on fast reconnection. An innovative aspect of the code is that it has been adapted for cell-based computers which are likely to be the future of large-scale computations with expected speed gains of a factor of 40 over existing simulations. The project will examine several important questions related to magnetic reconnection that are relevant to the Geospace Environment Modeling program's focus groups. The specific topics to be investigated include: (1) the relative roles of anti-parallel reconnection versus component merging, (2) the role of plasma turbulence on the rate of reconnection, (3) the dependence of the onset of reconnection and its subsequent nonlinear development on the plasma beta parameter (the ratio of the plasma pressure to the magnetic pressure), and (4) the evolution of asymmetric current sheets in the reconnection region. The educational aspects of the project includes support for several undergraduate students at UCSD to participate in the research. Two graduate students at the University of Iowa will also be involved.