Stabilising effect of magnetic field line topology in plasmas

Simon Candelaresi (University of Glasgow)

Thursday 30th January 14:00-15:00 Maths 311B

Abstract

For laboratory and astrophysical plasmas, the presence of electric currents and the magnetic field strongly determines the dynamics of the system. Plasma motions generate the magnetic field, while the magnetic field acts on the plasma through the Lorentz force. Within this interplay, the magnetic field line topology has a strong effect on the behavior of the plasma, as it is conserved at high magnetic Reynolds numbers. For instance, two interlinked magnetic flux tubes in the shape of the Hopf link will not be able to dis-entangle and evolve into the topologically trivial single flux ring.
Hence, the topology has a stabilising effect on the plasma, which we can exploit when we study the buoyant rise of hot under-dense cavities in the intergalactic medium. There we see that we can stabilise the cavities and prevent them from being shredded through the Kelvin-Helmholtz instability by imposing an internal topologically non-trivial magnetic field.

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