Flux Ropes Induced by O+ Outflow in the Near-Earth Magnetotail:
Three-Dimensional Hybrid Simulations
Abstract
Spacecrafts observe signatures of duskside magnetic reconnection in the
Earth’s magnetotail associated with the presence of oxygen (O+) ions of
ionospheric origin. The exact role of O+ ions in mediating reconnection
remains largely unknown due to the local nature of observational
techniques. We analyze results from global three-dimensional hybrid
(kinetic ions, fluid electrons) simulations of O+ outflows and
demonstrate that oxygen ions, escaping from the top of the ionosphere
into the lobes, may cause disruptions on the duskside of the
proton-formed magnetotail, adding up to its turbulent, unsteady nature.
These O+ ions are shown to be capable of inducing magnetic flux ropes in
the current sheet that thins out towards the dusk flank of the
magnetotail due to Hall and ion diamagnetic effects. Unlike
magnetohydrodynamics (MHD) simulations, where dawn-dusk magnetotail
asymmetries may develop due to nonuniform ionospheric conductivity, the
hybrid simulations demonstrate duskside tail disruptions on much faster
ion gyroscales.