Comparative Examination of Ion Energization Mechanisms in Coalescing FTE-Type Flux Ropes
Abstract
We report comparison of Vlasiator kinetic global simulations and Magnetospheric Multiscale (MMS) in-situ measurements of ion acceleration mechanisms. In particular, we examine ion acceleration during the coalescence of two flux transfer event-type flux ropes (FTEs) at the magnetopause. The coalescence process allows neighboring FTEs to merge and create larger flux ropes via magnetic reconnection. The topological rearrangement of field lines at the x-line that forms where the FTEs touch produces a local release of magnetic energy that produces intense localized plasma heating and Alfvenic jetting. Further, the resulting merged flux rope is highly non-force free as evidenced by its initial non-cylindrical cross-section. MMS data demonstrates that inside the thin current sheet at the interface between the two merging FTEs, ions are thermalized (in this case, perpendicular cooling and parallel heating). Downstream of the X-line, the betatron process decelerates ions locally (< -5 mW/m3) while parallel energization mechanisms accelerate ions across the magnetic field pile-up region by the inductive reconnection electric field (> +10 nW/m3) and tension force (< +5 nW/m3). The resulting phase-space density is a 'flat-top' distribution for a wide range of energies (0.5 < E ion < 7.6 keV). These observational properties are compared to results from the hybrid-Vlasov global code Vlasiator, which show several magnetic island coalescence events at the magnetopause. Vlasiator demonstrates different ion acceleration mechanisms through its noise-free 3-dimensional ion velocity distributions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSM32A..08A
- Keywords:
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- 2723 Magnetic reconnection;
- MAGNETOSPHERIC PHYSICSDE: 2724 Magnetopause and boundary layers;
- MAGNETOSPHERIC PHYSICSDE: 2728 Magnetosheath;
- MAGNETOSPHERIC PHYSICSDE: 2784 Solar wind/magnetosphere interactions;
- MAGNETOSPHERIC PHYSICS