Three-Dimensional Topology of the Magnetic Field in the Solar Corona

Lee, Daniel Thomas (2018) Three-Dimensional Topology of the Magnetic Field in the Solar Corona. Doctoral thesis, University of Central Lancashire.

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This thesis investigates the topology of the magnetic field in the solar corona, due to a variety of source configurations and types. To fully understand the complex behaviour of the Sun's magnetic field, it is important to have a complete description of the features present in its structure.

The magnetic topologies due to network source configurations are investigated using both the point source description and the continuous source description. A series of case studies involving an emerging bipole in a hexagonal arrangement to simulate a supergranular cell are studied. This has a particular focus on the behaviour of coronal nulls located in the topology, and a particular case may form the underpinning of a model for polar plumes.

A new topological feature, called a null-like point, is defined by relaxing the definition of a magnetic null point. Separatix-like surfaces, originating from null-like points, allow quasi-separatrix layers to be found in magnetic topologies due to continuously distributed sources. The squashing factor, Q, is mapped across the source configuration, highlighting the locations of the quasi-separatrix layers.

Finally, an algorithm is developed which automatically detects and classifies magnetic events local to X-ray bright points (XBPs). Significant peaks are identified in the gradients of flux curves (positive, negative and absolute flux) local to XBP footpoints, allowing instances of flux emergence and cancellation to be identified and linked to the onset and demise of the XBPs studied. The algorithm correctly classifies 90% of all emergence and cancellation events related to the studied XBPs.

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