Statistics of magnetic reconnection and turbulence in Hall-MHD and hybrid-PIC simulations
Résumé
Properties of decaying Alfvenic plasma turbulence are investigated bymeans of two-dimensional Hall-magnetohydrodynamic and hybrid particle-in-cell numerical simulations. In most cases, spectral properties ofturbulent fluctuations find good agreement in both the numerical models.The power spectra of the magnetic field exhibit a double power-law withspectral index -5/3 at large, fluid scales and -3 at sub-ion scales,while for velocity fluctuations the spectral index at fluid scales is-3/2. In both models, the development of a turbulent cascade isconcurrently characterized by magnetic reconnection events that arefast, with inverse reconnection rates much smaller than thecharacteristic large-eddy turnover times. Moreover, these reconnectionevents trigger a direct energy transfer from large to sub-ion scales.This supports the existence of a reconnection-mediated turbulent regimeat sub-ion scales. We conclude that the Hall-MHD fluid descriptioncaptures to a large extent the transition of the turbulent cascadebetween the fluid and sub-ion scales.