Magnetic reconnection in heliospheric plasma

Abstract

Magnetic reconnection is a fundamental process in astrophysical and laboratory plasmas, with significant implications for solar flares, Coronal Mass Ejections (CMEs), and the Sun-Earth connection. Despite extensive research, the partitioning of magnetic energy during the energy conversion process and the mechanism of high-energy particle production near reconnection sites remain active areas of investigation. The focus of this thesis is to provide a comprehensive understanding of magnetic reconnection in heliospheric and magnetospheric plasma using magnetohydrodynamic (MHD) simulations. The first contribution to this thesis presents resistive-MHD simulations of high Lundquist number current sheets in a double tearing mode (DTM) configuration with shear flow, investigating its effects on the linear and explosive non-linear phases of the reconnection process. The reconnection rates during the early phase match theoretical predictions, but deviations are observed during the explosive phase due to interactions between the layers and a structure driven feedback effect from large magnetic islands. The size and structure of the primary magnetic islands play a crucial role in determining the reconnection rate for different shear speeds. The scaling of the reconnection rate with shear holds true even during the non-linear phases of DTM evolution if the island sizes are taken into account. Analysis of test particles injected into the domain reveals different acceleration mechanisms for slightly, moderately, and highly accelerated particles.