Subion-scale turbulence driven by Magnetic Reconnection

The interplay between plasma turbulence and magnetic reconnection remains an unsettled question in astrophysical and laboratory plasmas. Here we report the first observational evidence that magnetic reconnection drives subion-scale turbulence in magnetospheric plasmas by transferring energy to small scales. We employ a spatial coarse-grained model of Hall magnetohydrodynamics, enabling us to measure the nonlinear energy transfer rate across scale ℓ at position x. Its application to Magnetospheric Multiscale mission data shows that magnetic reconnection drives intense energy transfer to subion-scales. This observational evidence is remarkably supported by the results from Hybrid Vlasov-Maxwell simulations of turbulence to which the coarse-grained model is also applied. These results open new pathways to investigate the interplay between turbulence, reconnection and energy dissipation in collisionless magnetized plasmas and can potentially explain spacecraft observations in various planetary magnetosheaths that showed the ubiquity of turbulent fluctuations at sub-ion scales even when no energy cascade emerges from the larger (MHD) scales.