Flux Ropes Induced by O + ${\mathrm{O}}^{+}$ 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 $\left(O^{+}\right)$ 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 toward the dusk flank of the magnetotail due to Hall and ion kinetic 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.