Three dimensional density cavities in guide field collisionless magnetic reconnection

TL;DR

This paper uses particle-in-cell simulations to reveal three-dimensional low-density structures, called cavities and ribs, in guide field collisionless magnetic reconnection, showing their formation, dynamics, and electric field support.

Contribution

It is the first to identify and describe the 3D features of cavities and low density ribs in guide field magnetic reconnection through simulations.

Findings

Development of low density ribs within cavities.

Ribs are supported by oscillating perpendicular electric fields.

Bipolar electric structures form between cavities and outflow plasma.

Abstract

Particle-in-Cell simulations of collisionless magnetic reconnection with a guide field reveal for the first time the three dimensional features of the low density regions along the magnetic reconnection separatrices, the so-called "cavities". It is found that structures with further lower density develop within the cavities. Because their appearance is similar to the rib shape, these formations are here called "low density ribs". Their location remains approximately fixed in time and their density progressively decreases, as electron currents along the cavities evacuate them. They develop along the magnetic field lines and are supported by a strong perpendicular electric field that oscillates in space. In addition, bipolar parallel electric field structures form as isolated spheres between the cavities and the outflow plasma, along the direction of the low density ribs and of magnetic field lines.