Magnetic Reconnection inside a Flux Transfer Event-like structure in
Magnetopause Kelvin-Helmholtz Waves
Abstract
Magnetopause Kelvin-Helmholtz (KH) waves are believed to mediate solar
wind plasma transport via small-scale mechanisms. Vortex-induced
reconnection (VIR) was predicted in simulations and recently observed
using NASA’s Magnetospheric Multiscale (MMS) mission data. Flux Transfer
Events (FTEs) produced by VIR at multiple locations along the periphery
of KH waves were also predicted in simulations but detailed observations
were still lacking. Here we report MMS observations of an FTE-type
structure in a KH wave trailing edge during KH activity on 5 May 2017 on
the dawnside flank magnetopause. The structure is characterised by (1)
bipolar magnetic BY variation with enhanced core field BZ and (2)
enhanced total pressure with dominant magnetic pressure. The
cross-section size of the FTE is found to be consistent with
vortex-induced flux ropes predicted in the simulations. Unexpectedly, we
observe an ion jet (VY), electron parallel heating, ion and electron
density enhancements, and other signatures that can be interpreted as a
reconnection exhaust at the FTE central current sheet. Moreover, pitch
angle distributions of suprathermal electrons on either side of the
current sheet show different properties, indicating different magnetic
connectivities. This FTE-type structure may thus alternatively be
interpreted as two interlaced flux tubes with reconnection at the
interface as reported by Kacem et al. (2018) and Øieroset et al. (2019).
The structure may be the result of interaction between two flux tubes,
likely produced by multiple VIR at the KH wave trailing edge, and
constitutes a new class of phenomenon induced by KH waves.