Magneto-Fluid Dynamics Seminar

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Suppression of electron thermal conduction by whistler turbulence in a sustained thermal gradient

Speaker: Gareth Roberg-Clark, University of Maryland College Park

Location: Warren Weaver Hall 905

Date: Tuesday, November 28, 2017, 11 a.m.

Synopsis:

We explore the dynamics of weakly magnetized collisionless plasmas in the presence of an imposed temperature gradient along an ambient magnetic field with particle-in-cell simulations and modeling. Two thermal reservoirs at different temperatures drive an electron heat flux that destabilizes off-angle whistler-type modes. The whistlers grow to large amplitude (fluctuation size comparable to the background B field), resonantly scattering the electrons and significantly reducing the heat flux. A surprise is that the resulting steady state heat flux is largely independent of the thermal gradient. The rate of thermal conduction is instead controlled by the finite propagation speed of the whistlers, which act as mobile scattering centers that convect the thermal energy of the hot reservoir. The results are relevant to thermal transport in high β astrophysical plasmas such as hot accretion flows and the intracluster medium of galaxy clusters.