SMS scnews item created by Lachlan Smith at Mon 27 Jul 2020 1428
Type: Seminar
Distribution: World
Expiry: 21 Sep 2020
Calendar1: 31 Jul 2020 1600-1700
CalLoc1: Zoom
Auth: (lsmi9789) in SMS-WASM

Sydney Dynamics Group: David Pfefferle -- What do spinning tops and flowing plasmas have in common?

Dear all, 

This week, Friday July 31, David Pfefferle (UWA) will give a talk at 4pm (Sydney time)
via Zoom.  

Zoom link: 

Meeting ID: 999 4684 6236 

Title: What do spinning tops and flowing plasmas have in common? 


At a macroscopic level, a plasma is suitably described by magneto-hydrodynamics (MHD)
equations or extensions thereof.  The hotter a plasma, the less resistive it is (the
opposite of a metal), becoming an ideal conductor in the infinite temperature limit.
Ideal MHD equations are relevant to the modelling of magnetic confinement fusion
plasmas, the heliosphere, solar flares, accretion disks, etc.  They feature several
structural properties leading to important conservation laws, in particular Alfvén’s
frozen-in theorem where the magnetic field is dragged along the plasma fluid motion.  It
is interesting to interpret the ideal MHD equations as the Euler-Poincaré equations
obtained by reduction of geodesic motion on the Lie-Fréchet group of diffeomorphisms
equipped with a right-invariant Riemannian metric.  The advantages of attaching a
variational problem to ideal MHD are theoretical (origins of relabelling symmetry and
conservation laws) and computational (hints for better discretisation schemes).  In this
talk, we will review Euler-Poincaré reduction using rigid body dynamics as an example,
we will apply the recipe to the ideal MHD problem, and discuss whether Multi-Region
relaXed magnetohydrodynamics (MRxMHD) fits in this picture.  

Past talks can be found on the YouTube channel: 

I hope to see you all online.  


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