Earth’s geospace environment incorporates a dynamic population of near-relativistic electrons trapped on magnetic field lines that extend out to geosynchronous orbit known as the Outer Radiation Belt (ORB). These electrons can damage spacecraft components and even cause terminal spacecraft failures thus forecasting and nowcasting the conditions in the ORB are critical to spacecraft operations.
The number of energetic electrons in the ORB determined from a combination of acceleration and loss processes. Electromagnetic waves can cause electrons to diffuse inwards across magnetic field-lines, causing the electrons to gain energy. At the same time, other electromagnetic wave populations can scatter the electrons into the atmospheric loss cone, causing the particles to precipitate into the upper atmosphere.
Current physics-based models of the radiation belts require global, statistical maps of electromagnetic waves to drive the dynamics of the ORB. However, these maps are commonly parameterised by geomagnetic indices which can take the same values during periods of net electron loss or acceleration within the ORB, such as during the main and recovery phases of storms respectively. As such, the models can be using the same wave populations to attempt to model different net changes in the ORB. This leads to two fundamental questions: “what are the electromagnetic wave populations during different net changes in the ORB and what dictates these changes?” and “are the wave populations or gradients in the particle populations the dominant factor in radiation belt dynamics?”.
Observations of the total number of energetic electrons in the radiation belt from the NASA Van Allen Probes mission hint that the changes in the radiation belt can be categorised as either rapid loss, rapid acceleration, or steady loss. Using a combination of in-situ and ground-based measurements, we will challenge the common parameterisation of the wave populations by re-casting the wave and particle distributions in terms of whether the ORB is undergoing rapid loss, steady loss or acceleration and revealing statistically significant differences between them. We will also examine whether categorising the waves in the same wave can improve physical models of the radiation belts.
This project will involve the examination of a variety of data sources including in-situ observations from missions such as Van Allen Probes, Arase and SAMPEX as well as ground-based data from magnetometer chains. Existing publicly available models will be adapted to examine the impact of the new results.
Desired Knowledge and Skills
- Undergraduate degree in Physics, with a strong interest in solar or space plasma physics.
- Strong computational skills in a relevant programming language (IDL, Matlab, Python).
- Good statistical and mathematical skills.
For details of how to apply please refer to our website: PhD Opportunities | UCL Department of Space and Climate Physics - UCL – University College London.
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