Ion-Mediated Tearing and Kink Instabilities in the Earth's Magnetosphere: Hybrid-Vlasov Simulations

We explore the three-dimensional structure of ion-kinetic instabilities in a thin current layer using a hybrid-Vlasov simulation of the Earth's magnetosphere. The simulation shows the simultaneous growth of tearing and kinking instabilities, which develop in the Sun-Earth and dawn-dusk directions, respectively, within the magnetotail current sheet. The formation of flux ropes indicates the development of the tearing instability, while flapping-type cross-tail oscillations arise from the kink instability. We consider both instabilities as independent polarizations, albeit sharing a common source: demagnetized ions forming crescent-shape distributions at the center of the current layer. These oscillations exhibit spatiotemporal characteristics within the proton-scale range, featuring a growth time on the order of 40–80 proton gyroperiods and a wavelength of approximately 15–30 proton skin depths.