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Effects of field-aligned currents in the ionosphere-thermosphere system

Hood, Rosie K. E.; (2018) Effects of field-aligned currents in the ionosphere-thermosphere system. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Space weather is one of the most significant natural hazards to modern day civilisation, posing a risk to both space and ground infrastructure. It describes the near-Earth and terrestrial environment as affected by the Sun, namely as a result of radiation, interactions with the interplanetary magnetic field and plasma outflow, the latter termed the solar wind. Field-aligned currents (FACs), that is, solar wind-driven currents aligned with the Earth’s geomagnetic field and closed in its ionosphere, play an essential role in the transfer of energy and circulation between the solar wind and the ionosphere-thermosphere system. We study two main consequences of FACs in this system: the induced ground geomagnetic disturbances (GMDs), which arise as FACs close in the ionosphere, and the resultant Joule heating and perturbed thermospheric neutral winds as the energy transferred by FACs dissipates via their closure currents. We find, within data restrictions, no strong linear correlation between FAC and GMD magnitudes, instead suggesting solar wind parameters as a better indication of the location and strength of harmful ground GMDs. We probe the effect a neutral wind disparity between ground-based instrument and satellite measurements will have on the distribution and magnitude of wind-derived Joule heating, after using a model to show the winds should be equivalent. We suggest the cause of the disparity is due to uncertainties in the satellite wind derivation. Finally, we investigate small-scale FAC-driven Joule heating and electron precipitation as the causes of a satellite-measured cusp density enhancement and FPI-measured cusp and nightside auroral oval upwellings. We model an empirical heating source representative of soft and hard precipitation in these regions. Our simulations support a mechanism of soft precipitation and Joule heating in the cusp but are unable to reproduce the nightside upwelling. We suggest this is a storm-related anomaly, requiring an adjusted mechanism.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Effects of field-aligned currents in the ionosphere-thermosphere system
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2018. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10064231
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