Micro-macro coupling in plasma self-organization processes during island coalescence

The collisionless island coalescence process is studied with particle-in-cell simulations, as an internal-driven magnetic self-organization scenario. The macroscopic relaxation time, corresponding to the total time required for the coalescence to complete, is found to depend crucially on the scale of the system. For small-scale systems, where the macroscopic scales and the dissipation scales are more tightly coupled, the relaxation time is independent of the strength of the internal driving force: the small-scale processes of magnetic reconnection adjust to the amount of the initial magnetic flux to be reconnected, indicating that at the microscopic scales reconnection is enslaved by the macroscopic drive. However, for large-scale systems, where the micro-macro scale separation is larger, the relaxation time becomes dependent on the driving force.