Scaling of asymmetric magnetic reconnection: General theory and collisional simulations

TLDR

Observational signatures and applications to magnetospheric reconnection are discussed. A Sweet‑Parker scaling analysis of asymmetric antiparallel reconnection is performed and its laws verified by 2‑D resistive MHD simulations of asymmetric fields with symmetric density. First‑principles scaling laws for reconnection rate, outflow speed, outflow density, and dissipation‑region structure are derived, are independent of the dissipation mechanism, and reveal that the X‑line and stagnation point are displaced, causing bulk plasma flow across the X‑line.

Abstract

A Sweet-Parker-type scaling analysis for asymmetric antiparallel reconnection (in which the reconnecting magnetic field strengths and plasma densities are different on opposite sides of the dissipation region) is performed. Scaling laws for the reconnection rate, outflow speed, the density of the outflow, and the structure of the dissipation region are derived from first principles. These results are independent of the dissipation mechanism. It is shown that a generic feature of asymmetric reconnection is that the X-line and stagnation point are not colocated, leading to a bulk flow of plasma across the X-line. The scaling laws are verified using two-dimensional resistive magnetohydrodynamics numerical simulations for the special case of asymmetric magnetic fields with symmetric density. Observational signatures and applications to reconnection in the magnetosphere are discussed.