Turbulent mass transfer caused by vortex induced reconnection in collisionless magnetospheric plasmas

T K M Nakamura,W Daughton,W Y Li,H Hasegawa,R Nakamura,S Eriksson

doi:10.1038/s41467-017-01579-0

Abstract

Magnetic reconnection is believed to be the main driver to transport solar wind into the Earth’s magnetosphere when the magnetopause features a large magnetic shear. However, even when the magnetic shear is too small for spontaneous reconnection, the Kelvin–Helmholtz instability driven by a super-Alfvénic velocity shear is expected to facilitate the transport. Although previous kinetic simulations have demonstrated that the non-linear vortex flows from the Kelvin–Helmholtz instability gives rise to vortex-induced reconnection and resulting plasma transport, the system sizes of these simulations were too small to allow the reconnection to evolve much beyond the electron scale as recently observed by the Magnetospheric Multiscale (MMS) spacecraft. Here, based on a large-scale kinetic simulation and its comparison with MMS observations, we show for the first time that ion-scale jets from vortex-induced reconnection rapidly decay through self-generated turbulence, leading to a mass transfer rate nearly one order higher than previous expectations for the Kelvin–Helmholtz instability.

Highlights

Magnetic reconnection is believed to be the main driver to transport solar wind into the Earth’s magnetosphere when the magnetopause features a large magnetic shear
We show results from a kinetic simulation under realistic magnetopause conditions obtained from the Magnetospheric Multiscale (MMS) spacecraft which feature a superAlfvénic velocity shear and a weak magnetic shear to satisfy Eq
Past theoretical and numerical studies of the magnetopause suggest that a type of reconnection process, which is induced by the compression of the pre-existing magnetic shear layer by the Kelvin–Helmholtz instability (KHI) vortex flow, can give rise to efficient plasma transport along the reconnected field lines[17, 18]

Summary

Introduction

Magnetic reconnection is believed to be the main driver to transport solar wind into the Earth’s magnetosphere when the magnetopause features a large magnetic shear. When the boundaries have large magnetic shears, the dominant process is magnetic reconnection which causes very efficient transfer along the reconnected field lines[1,2,3,4], while in the limit of superAlfvénic velocity shear, the Kelvin–Helmholtz instability (KHI)[5,6,7] is believed to induce a considerable transport[8,9,10,11,12,13,14]. Past theoretical and numerical studies of the magnetopause suggest that a type of reconnection process, which is induced by the compression of the pre-existing magnetic shear layer (current sheet) by the KHI vortex flow, can give rise to efficient plasma transport along the reconnected field lines[17, 18]. The new large-scale 3D simulation demonstrates the turbulent development of VIR within the

Methods

Results

Conclusion