Space Physics Seminar winter-2016

Three-dimensional global hybrid simulation of the Earth’s magnetosphere

Three-dimension (3-D) global hybrid simulation model is developed and performed to investigate the whole Earth’s magnetosphere for the first time, with physics from the ion kinetic to the global Alfvenic convection scales. Under the pure southward interplanetary magnetic field (IMF), it is found that the dayside reconnection leads to the penetration of the dawn-dusk electric field through the magnetopause and thus a thinning of the plasma sheet, followed by the multiple X-line reconnection in the magnetotail. The following results are going to be presented: (1) The magnetotail reconnection layer is turbulent with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. (2) Hall electric fields in the thin current layer cause a systematic dawnward ion drift motion and thus a dawn-dusk asymmetry of the plasma sheet with a higher (lower) density on the dawnside (duskside). Correspondingly, more reconnection as well as the relevant phenomena occurs on the duskside. (3) A number of small-scale flux ropes (FRs) are generated through the multiple X-line reconnection. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of FR evolution: earthward/tailward propagation, coalescence, merging, and tilt. (4) The earthward propagating FRs become highly asymmetric due to the imbalance of the reconnection rates between the multiple X-lines. The earthward propagating asymmetric FRs can fully reproduce the observational features of the dipolarization fronts (DFs). Therefore, the earthward propagating FRs can be used to explain the observed DFs in the magnetotail. (5) A shear flow type instability is found on the duskside flank of the ring current plasma, whereas a kinetic ballooning instability appears on the dawnside. (6) Ion velocity distributions and energy spectra reveal multiple beams/populations and energization at various regions in the magnetotail.