Flux ropes at the earth’s magnetopause: an investigation with the magnetospheric multiscale mission
File(s)
Author(s)
Robertson, Sadie L.
Type
Thesis
Abstract
Magnetic reconnection is a fundamental plasma physics process and takes place in space plasma environments throughout the solar system. During the process, magnetic field lines break and reconnect, allowing different plasma populations to mix and releasing energy stored in the magnetic field, which heats and accelerates particles. This change in magnetic field topology allows the production of helical magnetic field structures known as flux ropes. Here, we use data from NASA’s Magnetospheric Multiscale (MMS) mission to investigate the properties of magnetopause flux ropes, how they relate to the ongoing reconnection, and how they could facilitate energy transfer during magnetic reconnection.
This thesis presents a statistical survey of flux ropes associated with encounters of the magnetopause electron diffusion region (EDR), which is the central location where magnetic reconnection takes place. We find that the 245 identified EDR-associated flux ropes are smaller and have less flux content than previously reported, and that their properties vary with proximity to the EDR. This suggests that we are studying a distinct set of flux ropes that are potentially newly formed by the EDR.
The evolution and dynamics of the flux ropes are investigated by applying a force-free flux rope model. We find that the flux ropes generally show good agreement with the model, potentially being more force-free when they have larger radii and stronger axial fields. We also investigate the flux rope topology, finding that most flux ropes have an open topology and that closed topology observations are potentially correlated with a negative IMF BY component.
Finally, two case studies of electron trapping in magnetic mirror structures on the edge of magnetopause flux ropes are presented. These observations present a unique acceleration mechanism for flux ropes, and therefore magnetic reconnection more generally, highlighting the importance of such substructure for energy transfer during reconnection.
This thesis presents a statistical survey of flux ropes associated with encounters of the magnetopause electron diffusion region (EDR), which is the central location where magnetic reconnection takes place. We find that the 245 identified EDR-associated flux ropes are smaller and have less flux content than previously reported, and that their properties vary with proximity to the EDR. This suggests that we are studying a distinct set of flux ropes that are potentially newly formed by the EDR.
The evolution and dynamics of the flux ropes are investigated by applying a force-free flux rope model. We find that the flux ropes generally show good agreement with the model, potentially being more force-free when they have larger radii and stronger axial fields. We also investigate the flux rope topology, finding that most flux ropes have an open topology and that closed topology observations are potentially correlated with a negative IMF BY component.
Finally, two case studies of electron trapping in magnetic mirror structures on the edge of magnetopause flux ropes are presented. These observations present a unique acceleration mechanism for flux ropes, and therefore magnetic reconnection more generally, highlighting the importance of such substructure for energy transfer during reconnection.
Version
Open Access
Date Issued
2022-03
Date Awarded
2022-08
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Eastwood, Jonathan
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)