Do dispersive waves play a role in collisionless magnetic reconnection?
Using fully kinetic simulations, we demonstrate that the properly normalized reconnection rate is fast ∼0.1 for guide fields up to 80× larger than the reconnecting field and is insensitive to both the system size and the ion to electron mass ratio. These results challenge conventional explanations of reconnection based on fast dispersive waves, which are completely absent for sufficiently strong guide fields. In this regime, the thickness of the diffusion layer is set predominantly by the electron inertial length with an inner sublayer that is controlled by finite gyro-radius effects. As the Alfvén velocity becomes relativistic for very strong guide fields, the displacement current becomes important and strong deviations from charge neutrality occur, resulting in the build-up of intense electric fields which absorb a portion of the magnetic energy release. Over longer time scales, secondary magnetic islands are generated near the active x-line while an electron inertial scale Kelvin-Helmholtz instability is driven within the outflow. These secondary instabilities give rise to time variations in the reconnection rate but do not alter the average value.
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
- SciberQuest, Del Mar, California 92014 (United States)
- (United States)
- Space Science Institute, Boulder, Colorado 80301 (United States)
- Publication Date:
- OSTI Identifier:
- Resource Type:
- Journal Article
- Resource Relation:
- Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
- Country of Publication:
- United States
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ELECTRIC FIELDS; ELECTRONS; HELMHOLTZ INSTABILITY; MAGNETIC ISLANDS; MAGNETIC RECONNECTION; RELATIVISTIC RANGE; SIMULATION