Statistics of magnetic reconnection and turbulence in Hall-MHD and hybrid-PIC simulations

Properties of decaying Alfvenic plasma turbulence are investigated by means of two-dimensional Hall-magnetohydrodynamic and hybrid particle-in-cell numerical simulations. In most cases, spectral properties of turbulent fluctuations find good agreement in both the numerical models. The power spectra of the magnetic field exhibit a double power-law with spectral 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 is concurrently characterized by magnetic reconnection events that are fast, with inverse reconnection rates much smaller than the characteristic large-eddy turnover times. Moreover, these reconnection events trigger a direct energy transfer from large to sub-ion scales. This supports the existence of a reconnection-mediated turbulent regime at sub-ion scales. We conclude that the Hall-MHD fluid description captures to a large extent the transition of the turbulent cascade between the fluid and sub-ion scales.