Modelling Extreme Space Weather Events

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Space weather describes how activity on the Sun impacts our satellites in space and life here on Earth. The most extreme space weather events involve vast eruptions from the Sun, called "coronal mass ejections", or CMEs, which can travel towards Earth at millions of miles an hour. When they reach the influence of the Earth's magnetic field, the "magnetosphere", these CMEs trigger amazing auroral displays but can adversely affect satellites, communications and power grids. The coupled Sun-Earth system is, however, a complex dynamical environment with inter-related physical processes extending across scales ranging from less than a second to days, and from metres to millions of miles. Understanding and predicting the response of the magnetosphere, and trapped populations of energetic particles which form the hazardous "radiation belts", thus represents an immense challenge to the space physics and space weather communities, but one of increasing relevance as we move into the era of satellite mega-constellations and with humanity planning to establish a presence on the moon. This fellowship will focus on the modelling of extreme space weather events, using institutional and national high-performance-computing facilities. It is built upon three distinct recent advances; a heliospheric magnetohydrodynamic (MHD) model which can capture complex upstream phenomena originating at the Sun; the Gorgon MHD model which can capture the large-scale solar-wind-magnetosphere interaction; and an energetic Particle model which is integrated in Gorgon. The Particle model successfully scales to thousands of CPUs and can thus simulate ensembles of particles with characteristic sub-second timescales, across multi-day extreme space weather events. In order to understand the underlying physics, I will focus on a series of extreme events observed in the Space Age, as well as upcoming events during Solar Cycle 25 (2019-2030) where ESA's Solar Orbiter and NASA's Parker Solar Probe spacecraft are able to provide unprecedented insight from closer to the Sun.I will utilise this suite of simulation models to achieve three distinct goals: I will firstly comprehensively examine what solar wind conditions can rapidly create and destroy entire radiation belts. Following this, I will develop the advective Particle model to incorporate diffusive transport and tune this to match state-of-the art Fokker Planck Radiation Belt Models (RBMs). I will then directly identify and constrain advective transport processes, and determine appropriate diffusive-advective theories for improved radiation belt forecasting. Finally, I will self-consistently incorporate feedback from the particles into modified MHD equations, and study whether feedback from non-thermal particles produces a fundamentally different magnetospheric system or one that periodically diverges. This has far-reaching consequences for planetary magnetospheres and also extra-solar planetary magnetospheres where CMEs deriving from populous M stars play a significant role in defining habitability.