Plasma Physics Seminar

Dr. Seiji Zenitani, Goddard Space Flight Center "Resistive MHD studies of magnetic reconnection" and "A frame-independent measure of the dissipation region in collisionless magnetic reconnection" 1. Resistive magnetohydrodynamic simulations of relativistic magnetic reconnection Owning to growing attention to reconnection in extreme astrophysics, numerical modeling of relativistic reconnection has been growing in importance. In this talk, we study large-scale evolution of relativistic magnetic reconnection by using a modern MHD code. We demonstrate a Petschek-type reconnection with a fast Alfvenic outflow. We further discover new shock structures in and around the plasmoid. Influence of resistivity models and implications for nonrelativistic reconnection physics will be discussed. 2. A frame-independent measure of the dissipation region in collisionless magnetic reconnection The "diffusion region" or the "dissipation region" (DR) surrounding the reconnection site is of strong interest for understanding the key mechanism of reconnection. It is traditionally identified by the violation of the ideal condition, however, recent numerical results suggest that the ideal condition may not be a good identifier of the DR. In this work, we propose a new measure to identify the DR. We introduce the electron-frame dissipation measure, the energy transfer from the electromagnetic field to plasmas in the electron's rest frame. The theory, numerical tests by PIC simulations, and implications for nonideal MHD dissipation will be discussed. Return to main page