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Durham University

Research & business

Research lectures, seminars and events

The events listed in this area are research seminars, workshops and lectures hosted by Durham University departments and research institutes. If you are not a member of the University, but  wish to enquire about attending one of the events please contact the organiser or host department.


Applied mathematics seminar: Topological evolution and the equivalent unstirring problem in resistive magnetic relaxation

Presented by Long Chen, Durham University
27 November 2019 13:00 in TLC129/Zoom Meeting ID: 920 2546 6169 Passcode: 509245

Complex magnetic fields in plasmas may eventually relax to a simple state even if the resistivity is small. Nevertheless, what predicts the end state remains unclear. Using 3D magnetohydrodynamic (MHD) models, we find that there are two stages of topological evolution. The first is a fast reconnection phase constrained by the topological degree. The next is a slow phase dominated by diffusion and shows rearrangement and reconnection of discrete flux tubes. The end state always has two flux tubes with opposite twists, just as predicted by E. N. Parker.
Meanwhile, we find the topological change can also be studied in 2D effective models at a low computational cost. Interestingly, the structural change in the reduced model during the first stage is similar to the reverse process of fluid mixing. The overall reduction in complexity is consistent with an optimal unstirred state.

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