Identification of radiation belt drivers

Details

The Van Allen radiation belts are comprised of energetic particles moving at relativistic velocities that are trapped by the Earth’s magnetic field. The electrons in the radiation belts can vary by several orders of magnitude in short time scales, which can be devastating to spacecraft that transit the region. The energetic electrons are able to penetrate the spacecraft shielding and build up on the onboard electronics potentially resulting in electrical discharges that can cause the satellites to become inoperable. The variations in electron radiation belts are due to a balance of transport, acceleration and loss of the electrons, however, the exact mechanisms involved in these process and their external solar wind and geomagnetic drivers are still unclear.

The radiation belt system is highly complex and is difficult to model all the processes from the drivers to the variations in electron fluences from first principles. However, there are alternative data-driven approaches that are able to automatically deduce equations that link the input drivers to the system output from input-output data. The field of system identification has developed tools for deriving such mathematical models from data. A criticism that is often levied of these data-driven approaches is often due to the models lack of physical interpretation. They are described as “black boxes”, where it is not possible to understand how the inputs of the model couple together to result in the output and how to relate this back to the different underlying physical processes. The techniques of system identification not only allow for the deduction of accurate dynamical nonlinear models but will allow us to lift the lid of the “black box” to extract new physical understanding of the solar wind-radiation belts system.

The aim of this PhD project is to employ these methods of system identification to identify the solar wind and geomagnetic index parameters, and their time delays, that drive the variations of energetic electrons and develop models to forecast the electron fluences in the radiation belts. One of the challenges of the radiation belt system is that the electron populations do not just vary in time but also vary in space, energy and pitch angle. As such, the project will investigate how the electron flux drivers and their time delays change in the space, energy, and pitch angle to help uncover the physical processes that can potentially result in damage to spacecraft.