Explosive magnetic reconnection caused by an X-shaped current-vortex layer in a collisionless plasma

A mechanism for explosive magnetic reconnection is investigated by analyzing the nonlinear evolution of a collisionless tearing mode in a two-fluid model that includes the effects of electron inertia and temperature. These effects cooperatively enable a fast reconnection by forming an X-shaped curre...

Full description

Saved in:
Bibliographic Details
Published in:Physics of plasmas 2015-05, Vol.22 (5)
Main Authors: Hirota, M., Hattori, Y., Morrison, P. J.
Format: Article
Language:English
Subjects:
Collisionless plasmas
Computational fluid dynamics
Computer simulation
Nonlinear analysis
Plasma physics
Tearing
Two fluid models
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A mechanism for explosive magnetic reconnection is investigated by analyzing the nonlinear evolution of a collisionless tearing mode in a two-fluid model that includes the effects of electron inertia and temperature. These effects cooperatively enable a fast reconnection by forming an X-shaped current-vortex layer centered at the reconnection point. A high-resolution simulation of this model for an unprecedentedly small electron skin depth de and ion-sound gyroradius ρs, satisfying de=ρs, shows an explosive tendency for nonlinear growth of the tearing mode, where it is newly found that the explosive widening of the X-shaped layer occurs locally around the reconnection point with the length of the X shape being shorter than the domain length and the wavelength of the linear tearing mode. The reason for the onset of this locally enhanced reconnection is explained theoretically by developing a novel nonlinear and nonequilibrium inner solution that models the local X-shaped layer, and then matching it to an outer solution that is approximated by a linear tearing eigenmode with a shorter wavelength than the domain length. This theoretical model proves that the local reconnection can release the magnetic energy more efficiently than the global one and the estimated scaling of the explosive growth rate agrees well with the simulation results.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.4921329