First Demonstration of Anisotropic Fluid Closure Capturing the Kinetic Structure of Magnetic Reconnection

Magnetic reconnection is a process in weakly collisional plasmas that allows magnetic stresses to be reduced by a rearrangement of the magnetic field-line topology. This process is often accompanied by a large release of magnetic field energy, which can heat the plasma, drive large scale flows, or accelerate particles. Reconnection is the driver of explosive events such as solar flares, coronal mass ejections, magnetic substorms in the Earth’s magnetic tail, and sawtooth crashes in tokamaks. Reconnection has been widely studied through fluid models and kinetic simulations. While fluid models often reproduce the fast reconnection that is observed in nature and seen in kinetic simulations, significant differences are observed in the structure of the reconnection regions. Here we present results of fluid simulation implementing new equations of state for guide-field reconnection. The new fluid closure accurately account for the anisotropic electron pressure that builds in the reconnection region due to electric and magnetic trapping of electrons. In contrast to previous fluid models, our fluid simulation reproduces the detailed reconnection region as observed in fully kinetic simulations. We hereby demonstrate that the new fluid closure self-consistently captures all the physics relevant to the structure of the reconnection region, providing a gateway to a renewed and deeper theoretical understanding of reconnection in weakly collisional regimes.