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

Abstract

The dynamics of weakly magnetized collisionless plasmas in the presence of an imposed temperature gradient along an ambient magnetic field is explored 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, $\delta B/B_0\simeq 1$, and resonantly scatter the electrons, 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 $\beta$ astrophysical plasmas such as hot accretion flows and the intracluster medium of galaxy clusters.

Accepted for publication in Physical Review Letters. 5 pages, 5 figures. Supplementary material: 1 page, 1 figure

References in corpus (4)

• Magnetorotational Turbulence and Dynamo in a Collisionless Plasma
• Electron Heating by the Ion Cyclotron Instability in Collisionless Accretion Flows. I. Compression-Driven Instabilities and the Electron Heating Mechanism
• Nonlinear mirror instability
• Electron Heating by the Ion Cyclotron Instability in Collisionless Accretion Flows. II. Electron Heating Efficiency as a Function of Flow Conditions

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