Consolidated Grant in Solar Physics

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The physics of plasmas - particularly plasmas permeated by a magnetic field - dictates the behaviour of much of the visible universe. Close at hand, we need to understand and measure plasmas, fields and particles understand the dynamic Sun and its interaction with the heliosphere. In this proposal 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 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? 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? 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 lead to damaging `space weather'. Flares have distinctive radiation signatures that are closely related to the structure of the magnetic field, and 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 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 in which the plasma, and perhaps the magnetic field supporting it, is rotating.Our programme combines observational data with theoretical and numerical modelling to address all of these topics, and spans a wide range of astronomical and technical problems, from the modeling of the path of radiation in 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. Some aspects of our work will also help us to assess the potential threat of eruptions on the Sun, which is a key element of space weather forecasting.