Consolidated Grant in Solar Physics

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In this proposal we study the dynamic Sun, to measure and understand the plasmas, particles and processes in its atmosphere and the extended heliosphere that it creates. We focus on several key unsolved problems in solar physics, that are also prototypes for a wider and deeper understanding of cosmic plasmas as a whole. Our top-level questions are: How does the Sun store and release energy in its magnetised atmosphere, and what can we learn about this process by computer simulations and by studying the radiation that is emitted? How do high-energy radiating particles behave in solar flares and in interplanetary space? How are they accelerated, are they beamed and do they play a key role in flares and their terrestrial impact? The magnetic field is key to everything that happens in the Sun's atmosphere. Concentrated magnetic regions emerge through the Sun's surface and into its atmosphere. Here they interact with the pre-existing magnetic field and the result is intense bursts of energy known as flares, which accelerate sub-atomic particles (electrons and ions), cause heating to millions of degrees, and can also lead to expulsion of magnetised plasma into space, which can cause damaging `space weather'. Flares have distinctive radiation signatures that are closely related to the way that energy is transmitted along the magnetic field from the corona down to the solar surface and out into the distant heliosphere, and converted into other forms as it goes. By interpreting this radiation both from the Sun's tenuous outer atmosphere - its corona - and its denser lower atmosphere - its chromosphere - we can understand what is happening in a flare. More generally, solar magnetic fields create eccentric and dynamic shapes in the solar atmosphere, for example swirling `tornado-like' structures, and clouds of cool material called prominences, apparently floating (though in reality supported by magnetic forces) above the solar surface.Our programme combines observational data from space-based and ground-based telescopes with theoretical and numerical modelling to address all of these topics, and spans a wide range of technical problems, from the modeling of radiation moving through a plasma to high-energy particle acceleration; from electromagnetic waves to relativistic particle beams; from image processing to statistical analysis of weak signals, and from mathematical `pen-and-paper' calculations to advanced numerical simulations. We will bring all these skills to bear on questions at the heart of current efforts to better understand our nearest star.