Dynamics of Atmospheres and Magneto-Fluids in our Solar-Planetary Environment

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There has been tremendous development over the past decade, with further advances planned in the near future, in the observation and measurement of the Sun and the planetary bodies of the solar system. A huge amount of this progress has been made through space-based instruments, for example those on Cassini, Juno, Hinode, SDO, IRIS and Parker Solar Probe, but with the recent first light of DKIST ground-based instrumentation also has an important future role to play. As well as these new, and future (e.g. Solar Orbiter, Dragonfly) missions, the important data that is still being taken by older instruments, for example the long term magnetogram data that is being taken at Mount Wilcox Solar Observatory. This wealth of data makes study of the solar system a theorist's dream, where the high-quality data available provides important guidance and constraints on any theory being developed. Our proposed programme focuses on using theoretical and numerical studies to make detailed investigations of a huge range of important dynamical processes that occur across our solar system.In the area of Planetary physics we propose three studies looking at the atmospheric dynamics of three very different planetary bodies: Mars, Jupiter and Titan. The expertise in Exeter of modelling the Earth's atmosphere, strengthened by our close links with the nearby Met Office, will be further developed and extended as we investigate these three planetary bodies. We will use this expertise to investigate the role of Martian polar vortices, with their unusual 'annular' structure, in the formation of the striking water ice and dust layers at the poles of Mars. The atmospheric dynamics of Jupiter, as observed by Juno, discovered polar vortex crystals at the poles of Jupiter. The formation processes of this vortex structure will be tested. Titan, an important planetary body due to its similarity to Earth, has a thick nitrogen atmosphere and a hydrology cycle based on methane. We propose to investigate the drivers of Titan's general circulation and how it interacts with the methane cycle.The energy transferred to the magnetic field in the solar interior through the processes collectively known as the solar dynamo is the driver behind solar activity. Therefore, understanding the solar dynamo is a key step towards understanding both space climate and space weather, the latter of which is on the UK risk register. We will develop a new form of mean-field dynamo theory based on frequency averaging, unlike the classical theories that use averages in either space or time. By calculating the helicity flux at the photospheric boundary through theoretical and observational studies, we will obtain a consistent and thorough account of helicity balance in the Sun, providing constraints on the dynamo processes. Furthering this, new methods recently developed involving wavelets will be applied to understand the localisation of magnetic helicity.Magnetohydrodynamic turbulence in the solar corona and out into the solar wind is a hugely important process both in terms of transport (both of mass and energy) and in terms of dissipation. In the study of turbulence we propose two projects that focus on turbulent dynamics. The first studies the role of turbulence at the boundary between prominences (or spicules) and the solar corona, to understand the role of the turbulence in the thermodynamic evolution of the system. We will also investigate the turbulent energy cascade beyond the MHD scales through a study of Whistler wave interactions in Electron MHD.Finally, we shall communicate our work to the public and to schools, through the use of public lectures and workshops.