North-South asymmetric Kelvin-Helmholtz instability and induced reconnection at the Earth's magnetospheric flanks

TL;DR

This study uses three-dimensional two-fluid simulations to explore how asymmetric Kelvin-Helmholtz instabilities at Earth's magnetopause influence magnetic reconnection, revealing asymmetric vortex development and reconnection over a broad range of latitudes.

Contribution

It demonstrates the impact of magnetic shear and field line bending on asymmetric KH instability and reconnection locations at Earth's magnetopause during northward IMF conditions.

Findings

KH vortices develop asymmetrically relative to the equatorial plane.

Reconnection occurs at various latitudes, mainly in the less KH unstable hemisphere.

KH-induced reconnection can happen over a broad range of locations near vortices.

Abstract

We present a three-dimensional study of the plasma dynamics at the flank magnetopause of the Earth's magnetosphere during mainly northward interplanetary magnetic field (IMF) periods. Two-fluid simulations show that the initial magnetic shear at the magnetopause and the field line bending caused by the dynamics itself (in a configuration taken as representative of the properties of the flank magnetopause) influence both the location where the Kelvin-Helmholtz (KH) instability and the induced magnetic reconnection take place and their nonlinear development. The KH vortices develop asymmetrically with respect to the Earth's equatorial plane where the local KH linear growth rate is maximal. Vortex driven reconnection processes take place at different latitudes, ranging from the equatorial plane to mid-latitude regions, but only in the hemisphere that turns out to be the less KH unstable. These results suggest that KH-induced reconnection is not limited to specific regions around the vortices (inside, below or above), but may be triggered over a broad and continuous range of locations in the vicinity of the vortices.