The role of reconnection in MHD and kinetic turbulence

This work revisits the current understanding of Alfvénic turbulence to account for the role of magnetic reconnection. Theoretical arguments suggest that reconnection inevitably becomes important in the inertial range, at the scale where it becomes faster than the eddy turn over time. This leads to a transition to a new sub-inertial interval, suggesting a route to energy dissipation that is fundamentally different from that envisioned in the usual Kolmogorov-like phenomenology.

These concepts can be extended to weakly collisional plasmas, where reconnection is enabled by electron inertia rather than resistivity. Although several different cases must then be considered (whether the eddies themselves are on MHD or kinetic scales, whether the plasma beta is large or small, etc.), a common result to all of them is that the energy spectrum exhibits a scaling with the perpendicular wave number that scales between k_⊥^-8/3 and k_⊥^-3, in favorable agreement with many numerical results and observations.

This talk aims to review these results.