Solar electron and radio propagation in the turbulent solar corona

Alcock, Benjamin Thomas (2018) Solar electron and radio propagation in the turbulent solar corona. PhD thesis, University of Glasgow.

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Abstract

During a solar flare, ambient electrons are accelerated up to extremely high energies, producing a myriad of electromagnetic emission. Downwards travelling electron beams generate Hard X-rays (HXR) via interactions with the dense chromospheric plasma, while upwards propagating beams generate Langmuir waves which, in turn, cause the production of type-III radio emission.
This thesis is concerned with analysing observations and simulations of flare emission in order to learn about both the accelerated beam and the medium through which it travels.
Firstly, a comparison of in-situ detections of flare-accelerated electrons and inferred solar electrons is made, revealing differences in the populations. Electron transport along a turbulent magnetic field is simulated, and for the first time we find that, using constraints from HXR data, we are able to match simulations to observations at 1 AU.
Secondly, the effects of small and large-scale density inhomogeneities on the passage of low-frequency (32 MHz) radio photons is investigated. Monte-Carlo radio ray tracing simulations are used, and images from an observer at 1 AU are created. The effects of different heliospheric density and scattering profiles on produced images are analysed, and output images are compared to recent radio imaging results. We find that significant fluctuation and asymmetry levels produce apparent motion and growth of imaged radio sources, matching observations.
Finally, we use multi-spacecraft observations to locate the emission sources of several heliospheric (< 2 MHz) radio bursts. Significant enhancement of the source emission distance compared with predictions is found, and ray tracing simulations are used to model this. We find that significant density fluctuations in the heliosphere are able to produce outwards shifts of apparent sources, in good agreement with observations.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Solar physics, astronomy, radiative transfer, ray tracing, simulations, solar particle, turbulence, space physics, numerical modelling, solar radio, type-III burst.
Subjects: Q Science > QB Astronomy
Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
Funder's Name: Science & Technology Facilities Council (STFC)
Supervisor's Name: Kontar, Dr. Eduard
Date of Award: 2018
Depositing User: Mr Benjamin Alcock
Unique ID: glathesis:2018-9013
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 May 2018 08:48
Last Modified: 15 Jun 2018 12:13
URI: http://theses.gla.ac.uk/id/eprint/9013

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