Modulation of magnetic reconnection by the background plasma beta and guide field*

Magnetic reconnection is a pervasive plasma process, yet the exact conditions under which it occurs remain a subject of debate. Observational evidence suggests that the background plasma beta and magnetic shear angle are critical factors. In this study, we investigate how these factors influence the triggering of reconnection by examining the pinching dynamics of an initially non-equilibrium current sheet. Our findings indicate that a high plasma beta and guide field inhibit the pinching of the current sheet to kinetic scales necessary for collisionless reconnection, while low plasma beta and guide field facilitate this process. This hypothesis was validated through a systematic series of particle-in-cell simulations. Additionally, we derived a simple analytical model that predicts the parameter regions conducive to reconnection. Our results provide insights into the conditions that favor or hinder magnetic reconnection.