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NERSC Initiative for Scientific Exploration (NISE) 2010 Awards

Dependence of Secondary Islands in Magnetic Reconnection on Dissipation Model

Paul Cassak, West Virginia University

Associated NERSC Project: Three Dimensional and Diamagnetic Effects on the Onset and Evolution of Magnetic Reconnection Dimensions (m866), Principal Investigator: Paul Cassak

NISE Award: 200,000 Hours
Award Date: February 2010

Entropy colormap The physics of magnetic reconnection is a very important component of determining how energy gets released during solar eruptions, which contributes to our understanding of space weather. Magnetic reconnection is a fundamental plasma physics process that occurs in solar flares, the Earth's magnetosphere, and in fusion devices, which makes understanding it important for predicting space weather and producing a safe source of renewable energy. Reconnection allows magnetic field lines to break, which allows them to slingshot out and release large amounts of stored energy. Determining the rate at which magnetic reconnection releases energy is a topic of considerable importance to understanding how the energy is stored and released in such systems.

The original model of magnetic reconnection is called collisional, or Sweet-Parker reconnection. Upon its discovery, it was realized that it is very slow. However, this prediction came from assuming that current sheets that form during reconnection are structurally stable in the very extreme conditions in the solar corona. It has been known for some time that the current sheets are not structurally stable for coronal parameters and produce so-called secondary islands, but their role on the reconnection process has not been fully appreciated until recently. The question that needs to be answered is: "What is the effect of secondary islands on Sweet-Parker reconnection?"

Previous studies of secondary islands used simplified dissipation physics (a constant and uniform plasma resistivity). A careful study of the effect of this assumption on secondary island generation has not been carried out. We propose to test the dependence of secondary islands generation and their effect on reconnection as a function of resistivity model. In particular, we will use a Spitzer resistivity with and without self-consistent Ohmic heating and with and without viscosity, and compare the results of these simulations. These simulations will help us determine the extent to which what has been learned is applicable to real physical systems. These simulations are challenging because the computational domain needs to be resolved down to very small length scales.