What is the shortest possible x-line extent for 3D magnetic reconnection?
Abstract
In two-dimensional (2D) models, the extent of reconnection x-line is infinitely long because of the translational invariance in the direction out of the 2D plane. It is of great interest to understand the nature of a three-dimensional (3D) reconnection in the opposite limit. Notably, it remains unclear how a limited x-line extent would affect reconnection and whether there is a minimal requirement of x-line extent for fast reconnection.
Using 3D particle-in-cell (PIC) simulations, we explore this fundamental issue in a controlled fashion. We find that the reconnection rate and outflow speed drop significantly when the x-line extent is < O(10 di). If the x-line is long enough, we find it consists of two distinct regions. A suppression region (on the ion-drifting side) exists adjacent to an active region (on the electron-drifting side), where reconnection proceeds normally with a typical fast rate value 0.1. This is a consequence of the flux transport by electrons beneath the ion kinetic scale. The extent of the suppression region is ~ O(10 di), and it suppresses reconnection when the x-line extent is comparable or shorter. This study may explain the shortest azimuthal extent of dipolarizing flux bundles (DFBs) observed at Earth's magnetotail. It may also explain the dawn-dusk asymmetry of the DFB occurrence rate at Mercury's magnetotail, which is opposite to the asymmetry at Earth's magnetotail.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSM24B..10L
- Keywords:
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- 2723 Magnetic reconnection;
- MAGNETOSPHERIC PHYSICS;
- 2724 Magnetopause and boundary layers;
- MAGNETOSPHERIC PHYSICS;
- 2744 Magnetotail;
- MAGNETOSPHERIC PHYSICS;
- 7835 Magnetic reconnection;
- SPACE PLASMA PHYSICS