Tearing, Reconnection, and Anomalous Resistivity in a Mirror-infested Plasma

Various Larmor-scale kinetic instabilities can change the fundamental behavior of plasmas. To show this we study the time-dependent formation and evolution of a current sheet (CS) in a magnetized, collisionless, high-beta plasma using hybrid-kinetic particle-in-cell simulations. As the CS is thinned using a persistently driven incompressible shear flow, it becomes increasingly unstable to tearing while the strength of inflowing reconnecting field increases. Conservation of adiabatic invariance will then produces a field-based pressure anisotropy triggering mirror instability, which deforms the reconnecting field on ion-Larmor scales. These deformations are shown to accelerate the onset of reconnection via the tearing instability. In addition, using full particle-in-cell simulations, we assess the impact of various other Larmor-scale kinetic instabilities on the effective resistivity of a collisionless, high-beta plasma. These results find context in the structure of magnetic folds produced by the turbulent plasma dynamo, whose reversal scale is thought to be controlled by the plasma resistivity.