Ion versus Electron Heating in Compressively Driven Astrophysical Gyrokinetic Turbulence

Kawazura, Yohei; Schekochihin, A. A.; Barnes, Michael; TenBarge, Jason; Tong, Yuguang; Klein, K. G.; Dorland, W.

doi:10.1103/physrevx.10.041050

Cited by 35 publications

(52 citation statements)

References 73 publications

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“…This opposite behavior of T e and T p leads to a strong dependence of T e /T p on V sw . The ratio T e /T p is of great interest for local plasma processes since, e.g., the damping rate of ionacoustic waves and the energy partitioning of plasma heating are very sensitive to this parameter (Howes et al 2006;Schekochihin et al 2009Schekochihin et al , 2019Kawazura et al 2019Kawazura et al , 2020. We also note that the density and temperature behavior cause a significant dependence of the average β e on V sw , which is more pronounced than the dependence of β p on V sw .…”

Section: Discussionmentioning

confidence: 60%

Precision Electron Measurements in the Solar Wind at 1 au from NASA's Wind Spacecraft

Salem¹,

Pulupa²,

Bale³

et al. 2021

Preprint

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Context. The non-equilibrium characteristics of electron velocity distribution functions (eVDFs) in the solar wind are key in understanding the overall plasma thermodynamics as well as the origin of the solar wind. More generally, they are important in understanding heat conduction and energy transport in all weakly collisional plasmas. Solar wind electrons are not in Local Thermodynamic Equilibrium (LTE), and their multi-component eVDFs develop various non-thermal characteristics, such as velocity drifts in the proton frame, temperature anisotropies as well as suprathermal tails and heat fluxes along the local magnetic field direction. Aims. This work aims to characterize precisely and systematically the non-thermal characteristics of the eVDF in the solar wind at 1 au using data from the Wind spacecraft. Methods. We present a comprehensive statistical analysis of solar wind electrons at 1 au using the electron analyzers of the 3D-Plasma instrument on board Wind. This work uses a sophisticated algorithm developed to analyze and characterize separately the three populations -core, halo and strahl -of the eVDF up to super-halo energies (2 keV). This algorithm calibrates these electron measurements with independent electron parameters obtained from the quasi-thermal noise around the electron plasma frequency measured by Wind's Thermal Noise Receiver (TNR). The code determines the respective set of total electron, core, halo and strahl parameters through non-linear least-square fits to the measured eVDF, taking properly into account spacecraft charging and other instrumental effects, such as the incomplete sampling of the eVDF by particle detectors. Results. We use four years, approximately 280 000 independent measurements, of core, halo and strahl electron parameters to investigate the statistical properties of these different populations in the slow and fast solar wind. We discuss the distributions of their respective densities, drift velocities, temperature, and temperature anisotropies as functions of solar wind speed. We also show distributions with solar wind speed of the total density, temperature, temperature anisotropy and heat flux of the total eVDF, as well as those of the proton temperature, proton-to-electron temperature ratio, proton-β and electron-β. Intercorrelations between some of these parameters are also discussed. Conclusions. The present dataset represents the largest, high-precision, collection of electron measurements in the pristine solar wind at 1 AU. It provides a new wealth of information on electron microphysics. Its large volume will enable future statistical studies of parameter combinations and their dependencies under different plasma conditions.

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Section: Discussionmentioning

confidence: 60%

Precision Electron Measurements in the Solar Wind at 1 au from NASA's Wind Spacecraft

Salem¹,

Pulupa²,

Bale³

et al. 2021

Preprint

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“…Phenomenological models for electron and ion heating rates from Landau damping of Alfvénic turbulence were developed in the non-relativistic regime (Quataert 1998;Gruzinov 1998;Quataert & Gruzinov 1999;Howes 2010), and were broadly supported by recent hybrid gyrokinetic simulations (Kawazura et al 2019). Analytical theory also predicted that fast modes should preferentially heat ions in low β plasmas (Schekochihin et al 2019); this was subsequently confirmed by gyrokinetic simulations of compressively driven turbulence (Kawazura et al 2020). It is unclear how these results translate to the relativistic regime, where diffusive particle acceleration can absorb a significant fraction of the cascaded energy.…”

Section: Introductionmentioning

confidence: 87%

“…A more sophisticated prescription was proposed by Howes (2010), which has significant differences near β ∼ 1 and predicts preferential electron heating for β i 1 and T i /T e = 1, with preferential ion heating only at higher β i . Likewise, the empirical prescription in Kawazura et al (2020), based on gyrokinetic simulations, predicts preferential electron heating at these parameters. Note that these analytical models are inherently non-relativistic and therefore do not satisfy the necessary limit of ∆E int,e /∆E int,i = 1 for θ i 1 or for m i /m e → 1.…”

Section: Electron and Ion Energy Partitionmentioning

confidence: 99%

Particle energization in relativistic plasma turbulence: solenoidal versus compressive driving

Zhdankin

2021

Preprint

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Many high-energy astrophysical systems contain magnetized collisionless plasmas with relativistic particles, in which turbulence can be driven by an arbitrary mixture of solenoidal and compressive motions. For example, turbulence in hot accretion flows may be driven solenoidally by the magnetorotational instability or compressively by spiral shock waves. It is important to understand the role of the driving mechanism on kinetic turbulence and the associated particle energization. In this work, we compare particle-in-cell simulations of solenoidally driven turbulence with similar simulations of compressively driven turbulence. We focus on plasma that has an initial beta of unity, relativistically hot electrons, and varying ion temperature. Apart from strong large-scale density fluctuations in the compressive case, the turbulence statistics are similar for both drives, and the bulk plasma is described reasonably well by an isothermal equation of state. We find that nonthermal particle acceleration is more efficient when turbulence is driven compressively. In the case of relativistically hot ions, both driving mechanisms ultimately lead to similar power-law particle energy distributions, but over a different duration. In the case of non-relativistic ions, there is significant nonthermal particle acceleration only for compressive driving. Additionally, we find that the electron-to-ion heating ratio is less than unity for both drives, but takes a smaller value for compressive driving. We demonstrate that this additional ion energization is associated with the collisionless damping of large-scale compressive modes via perpendicular electric fields.

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“…The partition of energy between electrons and ions in MHD turbulence is a rather convoluted problem, which depends on a number of parameters, not only the initial magnetisation and species temperatures, but also the nature (compressive or Alfvénic) of the turbulence itself (e.g. Kawazura et al 2020). As of today, there exist only a few kinetic simulations of ionelectron turbulence in the regime of interest and we rely on the results of Zhdankin et al (2019).…”

Section: Appendix A: Electron Heating In Reconnection Layers or Magnetised Turbulencementioning

confidence: 99%

Electron-proton co-acceleration on relativistic shocks in extreme-TeV blazars

Zech

Lemoine

2021

A&A

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Aims. The multi-wavelength emission from a newly identified population of ‘extreme-TeV’ blazars, with Compton peak frequencies around 1 TeV, is difficult to interpret with standard one-zone emission models. Large values of the minimum electron Lorentz factor and quite low magnetisation values seem to be required. Methods. We propose a scenario where protons and electrons are co-accelerated on internal or recollimation shocks inside the relativistic jet. In this situation, energy is transferred from the protons to the electrons in the shock transition layer, leading naturally to a high minimum Lorentz factor for the latter. A low magnetisation favours the acceleration of particles in relativistic shocks. Results. The shock co-acceleration scenario provides additional constraints on the set of parameters of a standard one-zone lepto-hadronic emission model, reducing its degeneracy. Values of the magnetic field strength of a few mG and minimum electron Lorentz factors of 103 to 104, required to provide a satisfactory description of the observed spectral energy distributions of extreme blazars, result here from first principles. While acceleration on a single standing shock is sufficient to reproduce the emission of most of the extreme-TeV sources we have examined, re-acceleration on a second shock appears needed for those objects with the hardest γ-ray spectra. Emission from the accelerated proton population, with the same number density as the electrons but in a lower range of Lorentz factors, is strongly suppressed. Satisfactory self-consistent representations were found for the most prominent representatives of this new blazar class.

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Ion versus Electron Heating in Compressively Driven Astrophysical Gyrokinetic Turbulence

Cited by 35 publications

References 73 publications

Precision Electron Measurements in the Solar Wind at 1 au from NASA's Wind Spacecraft

Precision Electron Measurements in the Solar Wind at 1 au from NASA's Wind Spacecraft

Particle energization in relativistic plasma turbulence: solenoidal versus compressive driving

Electron-proton co-acceleration on relativistic shocks in extreme-TeV blazars

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