NERSC Initiative for Scientific Exploration (NISE) 2009 Awards

Onset of Collisionless Magnetic Reconnection in Weakly Collisional Plasmas

Paul Cassak, West Virginia University

Sponsoring NERSC Project: Onset and Evolution of Magnetic Reconnection in Three Dimensions (m866), Principal Investigator: Paul Cassak, West Virginia University

Magnetic reconnection is a fundamental plasma physics process that occurs in solar flares, the Earth's magnetosphere, and fusion devices. Understanding magnetic reconnection is important for predicting space weather and producing a safe source of renewable energy. Reconnection often begins abruptly, releasing large amounts of stored energy in a short time. Understanding the conditions under which magnetic reconnection begins is a topic of considerable importance to accomplish these goals.

There are two forms of reconnection, collisional and collisionless. It is known that the former is very slow, while the latter is very fast. It has been proposed that a transition between the two is responsible for the sudden onset typically observed in reconnection events. However, the generation of so-called secondary islands is known to make collisional reconnection faster and is expected to be ubiquitous in some applications such as solar flares. Previous studies considered the transition to collisionless reconnection without including secondary islands. We propose to include secondary islands in a simulation to investigate the onset of collisionless reconnection. We predict that secondary islands alter the collisional reconnection phase, but the full-fledged transition to collisionless reconnection remains a dramatic effect. These simulations are challenging because a single computational domain needs to contain both collisional and collisionless physics, which take place at vastly different length scales.