Pressure anisotropy can strongly influence the dynamics of weakly collisional, highbeta plasmas, but its effects are missed by standard magnetohydrodynamics (MHD). Small changes to the magneticfield strength generate large pressureanisotropy forces, heating the plasma, driving instabilities and rearranging flows, even on scales far above the particles’ gyroscales where kinetic effects are traditionally considered most important. Here, we study the influence of pressure anisotropy on turbulent plasmas threaded by a mean magnetic field (Alfvénic turbulence). Extending previous results that were concerned with Braginskii MHD, we consider a wide range of regimes and parameters using a simplified fluid model based on drift kinetics with heat fluxes calculated using a Landaufluid closure. We show that viscous (pressureanisotropy) heating dissipates between a quarter (in collisionless regimes) and half (in collisional regimes) of the turbulentcascade power injected at large scales; this does not depend strongly on either plasma beta or the iontoelectron temperature ratio. This will in turn influence the plasma's thermodynamics by regulating energy partition between different dissipation channels (e.g. electron and ion heat). Due to the pressure anisotropy's rapid dynamic feedback onto the flows that create it – an effect we term ‘magnetoimmutability’ – the viscous heating is confined to a narrow range of scales near the forcing scale, supporting a nearly conservative, MHDlike inertialrange cascade, via which the rest of the energy is transferred to small scales. Despite the simplified model, our results – including the viscous heating rate, distributions and turbulent spectra – compare favourably with recent hybridkinetic simulations. This is promising for the more general use of extendedfluid (or even MHD) approaches to model weakly collisional plasmas such as the intracluster medium, hot accretion flows and the solar wind.
 NSFPAR ID:
 10204599
 Date Published:
 Journal Name:
 Monthly Notices of the Royal Astronomical Society
 Volume:
 486
 Issue:
 3
 ISSN:
 00358711
 Page Range / eLocation ID:
 4013 to 4029
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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