Ion versus Electron Heating in Compressively Driven Astrophysical Gyrokinetic Turbulence

Y. Kawazura, A. A. Schekochihin, M. Barnes, J. M. Tenbarge, Y. Tong, K. G. Klein, W. Dorland

Research output: Contribution to journalArticlepeer-review

Abstract

The partition of irreversible heating between ions and electrons in compressively driven (but subsonic) collisionless turbulence is investigated by means of nonlinear hybrid gyrokinetic simulations. We derive a prescription for the ion-To-electron heating ratio Qi/Qe as a function of the compressive-To-Alfvénic driving power ratio Pcompr/PAW, of the ratio of ion thermal pressure to magnetic pressure βi, and of the ratio of ion-To-electron background temperatures Ti/Te. It is shown that Qi/Qe is an increasing function of Pcompr/PAW. When the compressive driving is sufficiently large, Qi/Qe approaches ≃Pcompr/PAW. This indicates that, in turbulence with large compressive fluctuations, the partition of heating is decided at the injection scales, rather than at kinetic scales. Analysis of phase-space spectra shows that the energy transfer from inertial-range compressive fluctuations to sub-Larmor-scale kinetic Alfvén waves is absent for both low and high βi, meaning that the compressive driving is directly connected to the ion-entropy fluctuations, which are converted into ion thermal energy. This result suggests that preferential electron heating is a very special case requiring low βi and no, or weak, compressive driving. Our heating prescription has wide-ranging applications, including to the solar wind and to hot accretion disks such as M87 and Sgr A∗.

Original languageEnglish
Article number041050
JournalPhysical Review X
Volume10
Issue number4
DOIs
Publication statusPublished - 2020 Dec 11

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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