RAS Ordinary Meeting

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End Date


Chris Davies (Scripps Institution of Oceanograph):
Powering the heat engine in Earth's core

Benjamin Joachimi (UCL):
Cosmology with galaxy shapes

2014 RAS James Dungey Lectureship: Professor Sandra C Chapman (University of Warwick): Reconnection and Turbulence: Thinking in Pictures

Ask anyone about Jim Dungey and reconnection and they are more than likely to make a sketch of magnetic field topology and dynamics. Topologies, symmetries, and dynamics are often easiest to see visually, in a series of drawings of snapshots of the magnetic field and flows. However, these sketches are more than illustrative, they are pictures that follow the rules of plasma electrodynamics and as such can be used as tools to further understanding.

Both reconnection and turbulence are ubiquitous in astrophysical fields and flows. They are key mechanisms for plasma heating and particle acceleration from the energy contained in large scale plasma flows and magnetic fields. A topical question is how turbulence and reconnection are related. Does turbulence enhance reconnection? Does reconnection modify the turbulence? What are the implications for plasma heating? These processes can be observed in-situ at first hand in our solar system using satellite-borne instrumentation. We now have a rich collection of such observations and in particular, multi-point and high time resolution observations are revealing new insights into reconnection and turbulence. Alongside this, it is now becoming feasible to perform numerical simulations that capture the full non-linear physics self-consistently down to kinetic scales, in three dimensions. Testing theory and simulations with data requires us to be quantitative, under the somewhat difficult circumstances of an observed natural system. The robust, reproducible features of turbulence are statistical. Tools developed to quantify the spatial texture of fractal patterns are used to quantify the statistical similarity of fluctuations in turbulent flows.
This talk will explore the intimate relationship between topology and physics in turbulence and reconnection, and what we can learn by thinking in pictures.