title: Laboratory observation of localized onset of magnetic reconnection.
abstract: Magnetic reconnection is a fundamental process in plasmas that results in the often explosive release of stored magnetic energy, but the trigger for its onset is not well understood. We explore this trigger for fast reconnection in toroidal experiments using a magnetic x-type geometry in the strong guide-field regime. We find that the onset occurs asymmetrically: the reconnection begins on one side of the torus and propagates around approximately at the Alfvén speed. The fast reconnection occurs only in the presence of a global plasma mode, which breaks the axisymmetry and enables the current at the x line to decrease sharply. A simple semiempirical model is used to describe the onset's growth rate.
authors.affiliation: Department of Physics/Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. nkatz@mit.edu
authors.forename: Noam
authors.initials: N
authors.lastname: Katz
authors.forename: Jan
authors.initials: J
authors.lastname: Egedal
authors.forename: Will
authors.initials: W
authors.lastname: Fox
authors.forename: Ari
authors.initials: A
authors.lastname: Le
authors.forename: Jeff
authors.initials: J
authors.lastname: Bonde
authors.forename: Arturs
authors.initials: A
authors.lastname: Vrublevskis