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 β 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 can potentially answer some open questions on
plasma turbulence in planetary environments