Estimating Proximity to the Asymmetric Reconnection X-line

Thesis Type:

phd

Abstract:

Magnetic reconnection is a process that changes magnetic topology, allows plasma transport across boundaries, and converts field potential energy to particle kinetic energy. All of these processes are tied to the X-line, or site of reconnection, yet current methods of locating the reconnection site either do not uniquely identify the the X-line or have not been tested when asymmetries in field strength and plasma density and temperature are present. Furthermore, identification of spacial structures (such as the X-line) as they traverse satellites is limited by hardware constraints. This thesis proposes a new method of locating the reconnection site for asymmetric magnetic reconnection (AMR), and an algorithm for merging fluxgate and searchcoil magnetometer datasets to improve data fidelity in a specific frequency range. Cluster observations show that asymmetries present during reconnection cause a variety of transitions in the reconnecting component of the magnetic field, ion density, ion outflow jets, and the normal component of the electric field across the magnetopause. Simulations in 2D and 3D and a laboratory experiment, both with and without guide field, contain similar offsets. Only within 5 electron inertial lengths of the X-line do transitions occur simultaneously. Farther away, transitions offset from one another in a systematic way. Electron distribution functions serve as an independent check of the method, as they take on a triangular shape that is unique to the X-line. Normal electric field offsets and outflow upstream from the X-line are linked to the presence of a guide field. This new methodology is applied to Cluster AMR events to demonstrate its use. One Cluster event in close proximity to the X-line exhibits triangle-shaped distributions and enhanced currents.

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