When: Friday, October 1, 2021, 2:30 PM - 3:30 PMWhere: Physics (G. O. Jones building) room 610 & online
Speaker: Clare Watt (Northumbria University)
Earth’s variable outer radiation belt: From microscale to macroscale
The near-Earth plasma environment is home to a highly variable region of high-energy electrons that is known as the outer radiation belt. The variability of the belt is driven by transient structures in the solar wind, such as coronal mass ejections and corotating interaction regions. The physical mechanisms for the variability of the high-energy electron flux in the outer radiation belt include the influence of wave-particle interactions, injections of high-energy electrons from the tail plasma sheet, and the action of sudden compressions on the magnetosphere. However, we don’t currently understand the system enough to be able to connect solar wind variability directly to radiation belt variations.
There is significant societal interest in our ability to predict the variability of the harsh radiation environment. Nowcasts and forecasts can provide crucial information to spacecraft operators in order to mitigate the effects of space weather on satellites. The terrestrial space plasma physics community in the UK is currently supported by UKRI to produce operational space weather forecasts of the radiation belts, among other space weather projects, and state-of-the-art models are being provided to the UK Met Office for operational use. In this talk, I want to talk about some of the scientific challenges in making predictions in a system where we don’t yet have full understanding. I will focus on the action of wave-particle interactions in the outer radiation belt. I will discuss how they change the motion of electrons in the collisionless plasma of the magnetosphere using microscale (kinetic) physics. I will then show how we try to include this microscale physics in macroscale (system-wide) descriptions. Using new results, I will demonstrate why the variability of these processes can be an important factor in our models. Finally, I hope to have time to discuss sources of natural variability in a plasma, and how understanding of natural plasma systems doesn’t necessarily have to involve deterministic processes.