UCLA

Magnetic reconnection is a fundamental physical process that happens between anti-parallel magnetic field components. This process is ubiquitous and can be found in both laboratory and space plasma. At the same time, it modifies the field topology and converts energy explosively from field to plasma. With its universality and capability, magnetic reconnection has been an important subject for decades, and with improving observation/modeling techniques, we are able to keep advancing our knowledge on this topic.

In this dissertation we utilize in-situ measurements from the Magnetospheric Multiscale (MMS) and numeric modeling. We first investigate the heart of magnetic reconnection, the X-line. Then we focus on the Flux Transfer Events (FTEs) which are products of magnetic reconnection on the Earth’s magnetopause and the interactions between flux ropes that carry the reconnected magnetic flux. We apply magnetic curvature analysis to the electron diffusion region (EDR) crossings and x-line crossings. We find highly increased magnetic curvature. The radius of curvature can decrease to the order of electron gyro-radius, which is consistent with the small scale nature of the center of magnetic reconnection. Another essential property of magnetic reconnection is the magnetic flux transport during the annihilation and reformation of magnetic field lines. We develop a new method to quantitatively describe the magnetic flux transport (MFT) characteristics and test it in both simulations and observations. We find bidirectional Alfvenic inflow and outflow of magnetic flux in a specially limited region around the X-line. This transport pattern defines reconnection and produces a new quadrupolar pattern in the divergence of the magnetic flux transport velocity. As the reconnected magnetic flux is carried away from the initial reconnection site in the FTE, we discover magnetic entanglement and new pairs of flux ropes are born through the disentanglement enabled by the reconnection between two entangled flux tubes. We further identify three temporal evolutionary stages of magnetic entanglement. Three-dimensional Hall Magnetohydrodynamic (MHD) simulation verifies the feasibility of this process and shows it is mainly driven by the momentum of the ambient converging plasma.