Kinetic Structure, Stability, and Dynamics of Current Sheets in Magnetospheric Plasmas

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

This project will develop and employ a new class of current sheet equilibria in Earth's magnetosphere. These equilibria will be analytic solutions and can be used initiate dynamical studies of their time evolution using particle-in-cell (PIC) kinetic simulations of the plasma. Among the issues that will be addressed are the following: Can the many observed current sheet configurations in Earth's magnetosphere be modeled by the stable members of this new class of equilibria? How sensitive is undriven (spontaneous) reconnection to initial conditions? What are the underlying instabilities which destabilize current sheets? How is magnetic reconnection triggered in Earth's magnetotail? How well can the initiation of asymmetric reconnection at Earth's magnetopause be modeled by the new equilibria? How well can the new equilibria model transient reconnection onset in the magnetotail? The PIC simulations in two and three dimensions will determine the stability of these diverse kinetic equilibria against a variety of plasma processes including tearing, lower hybrid drift and other instabilities. In addition, preliminary results have demonstrated that non-equilibrium initial conditions can lead to self-generated current sheets. The investigation of how non-equilibrium conditions can evolve toward an equilibrium condition will improve our understanding of the dynamics of the magnetosphere. The research has relevance to many different fields of plasma physics. Even within the main focus of magnetospheric physics the research will have diverse impacts. It will provide novel asymmetric kinetic current sheet equilibria for simulations of reconnection at the magnetopause as well as symmetric equilibria for a wider class of simulations of reconnection in the magnetotail and magnetosheath. Furthermore, it can contribute to our understanding of the many broad stable current sheets which have been observed in the magnetosphere and which cannot be modeled as Harris current sheet equilibria. Its potential impact extends to all plasma domains where collisionless magnetic reconnection occurs: to the magnetosphere, to the solar wind, to the solar corona, to laboratory reconnection experiments and to toroidal magnetic fusion devices in which "sawtooth" instabilities which inhibit confinement and heating are believed to involve reconnection. The project will also have an educational impact through the training of a graduate student in plasma theory, simulations, and data visualization.