Relaxation, Intermittency and Dissipation in a Collisionless Plasma

点击翻译按钮获取中文摘要

The purpose of this project is to improve understanding of the basic science of turbulence in a plasma. Turbulence is the complex dynamics of a fluid or gas resulting from nonlinear forces that span a wide range of scales in space and time. Many important effects emerge from turbulence, such as mixing and rapid transport of heat and energy; this influences terrestrial fluids as well as electrically conducting gases, or plasmas, in space and on the sun. Turbulence is usually not uniform in space – it tends to quickly self-organize into irregularly shaped "cells." Inside these cells the plasma is typically quiescent, but the thin boundaries between cells are highly active with sometimes explosive results. Processes causing this self-organization and formation of the cell boundaries are studied in this project. This effort will support a post-doctoral researcher and advance understanding of many observed space plasma phenomena, including solar flares and variability of turbulence in the solar wind, thus contributing to the science underlying space weather.Relaxation processes, turbulence cascade and dissipation mechanisms are each an important area of study in plasma physics and its applications. However these are most frequently studied separately. The fundamental hypothesis advanced in this project is that the nature of the intermittent cascade, and the dissipation that it leads to, are strongly influenced by specific relaxation processes that originate at the energy containing scales. In particular, local relaxation leads to spatial cellularization, and the associated spatial nonuniformity controls the formation of coherent structures, where dissipation is expected to be greatly enhanced. This has been studied, although incompletely, in fluid plasma models such as magnetohydrodynamics, but is poorly understood in fully kinetic plasma models to be considered within this project. Establishing such fundamental connections as parameters are changed to vary among modes of relaxation will advance understanding of fundamental plasma physics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.