Electron Heating by the Ion Cyclotron Instability in Collisionless Accretion Flows. II. Electron Heating Efficiency as a Function of Flow Conditions

Abstract

In the innermost regions of low-luminosity accretion flows, including Sgr A* at the center of our Galaxy, the frequency of Coulomb collisions is so low that the plasma is two-temperature, with the ions substantially hotter than the electrons. This paradigm assumes that Coulomb collisions are the only channel for transferring the ion energy to the electrons. In this work, the second of a series, we assess the efficiency of electron heating by ion velocity-space instabilities in collisionless accretion flows. The instabilities are seeded by the pressure anisotropy induced by magnetic field amplification, coupled to the adiabatic invariance of the particle magnetic moments. Using two-dimensional (2D) particle-in-cell (PIC) simulations, we showed in Paper I that if the electron-to-ion temperature ratio is < 0.2, the ion cyclotron instability is the dominant mode for values of ion beta_i ~ 5-30 (here, beta_i is the ratio of ion thermal pressure to magnetic pressure), as appropriate for the midplane of low-luminosity accretion flows. In this work, we employ analytical theory and 1D PIC simulations (with the box aligned with the fastest growing wavevector of the ion cyclotron mode) to fully characterize how the electron heating efficiency during the growth of the ion cyclotron instability depends on the electron-to-proton temperature ratio, the plasma beta, the Alfven speed, the amplification rate of the mean field (in units of the ion Larmor frequency) and the proton-to-electron mass ratio. Our findings can be incorporated as a physically-grounded sub-grid model into global fluid simulations of low-luminosity accretion flows, thus helping to assess the validity of the two-temperature assumption.

arXiv comment18 pages, 6 figures, 6 tables, 2 appendices, submitted to ApJ. Paper I appeared on Monday November 24th

References in corpus (31)

• Advection-Dominated Accretion: Underfed Black Holes and Neutron Stars
• Hot Accretion Flows Around Black Holes
• Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A*
• Relativistic Reconnection: an Efficient Source of Non-Thermal Particles
• Advection-Dominated Accretion Model of Sagittarius A*: Evidence for a Black Hole at the Galactic Center
• The Maximum Energy of Accelerated Particles in Relativistic Collisionless Shocks
• Turbulence and Particle Heating in Advection-Dominated Accretion Flows
• Particle Heating by Alfvenic Turbulence in Hot Accretion Flows
• Electron Heating in Hot Accretion Flows
• A Physical Relationship Between Electron-Proton Temperature Equilibration and Mach Number in Fast Collisionless Shocks
• Empirical Constraints on Proton and Electron Heating in the Fast Solar Wind
• Plasma instabilities and magnetic-field growth in clusters of galaxies
• Simulations of relativistic collisionless shocks: shock structure and particle acceleration
• Influence of Ohmic Heating on Advection-Dominated Accretion Flows
• Relativistic Pair Beams from TeV Blazars: A Source of Reprocessed GeV Emission rather than IGM Heating
• Local 2D Particle-in-cell simulations of the collisionless MRI
• Proton, Electron, and Ion Heating in the Fast Solar Wind from Nonlinear Coupling Between Alfvenic and Fast-Mode Turbulence
• A nonlinear theory of the parallel firehose and gyrothermal instabilities in a weakly collisional plasma
• Thermal X-Ray Iron Line Emission from the Galactic Center Black Hole Sagittarius A*
• Magnetic field amplification and evolution in turbulent collisionless MHD: an application to the ICM
• Acceleration of Relativistic Electrons by MHD Turbulence: Implications for Non-thermal Emission from Black Hole Accretion Disks
• Particle Acceleration during Magnetorotational Instability in a Collisionless Accretion Disk
• The Galactic Center Weather Forecast
• Apar-T: code, validation, and physical interpretation of particle-in-cell results
• Collisionless shock in a partially ionized medium. II. Balmer emission
• Radio light curves during the passage of cloud G2 near Sgr A*
• Dissipation in intercluster plasma
• Electron Heating by the Ion Cyclotron Instability in Collisionless Accretion Flows. II. Electron Heating Efficiency as a Function of Flow Conditions
• The Efficiency of Second-Order Fermi Acceleration by Weakly Compressible MHD Turbulence
• Particle Heating by Nonlinear Alfvenic Turbulence in ADAFs
• Linear theory of weakly amplified, parallel propagating, transverse temperature anisotropy instabilities in magnetized thermal plasmas

Cited by in corpus (29)

• The role of electron heating physics in images and variability of the Galactic Centre black hole Sagittarius A*
• Electron and proton heating in trans-relativistic magnetic reconnection
• Magnetorotational Turbulence and Dynamo in a Collisionless Plasma
• Suppression of electron thermal conduction by whistler turbulence in a sustained thermal gradient
• Laboratory Space Physics: Investigating the Physics of Space Plasmas in the Laboratory
• PIC Simulations of the Effect of Velocity Space Instabilities on Electron Viscosity and Thermal Conduction
• Astrophysical gyrokinetics: Turbulence in pressure-anisotropic plasmas at ion scales and beyond
• Electron and Proton Heating in Transrelativistic Guide Field Reconnection
• GRB Fermi-LAT afterglows: explaining flares, breaks, and energetic photons
• Multi-messenger tests of cosmic-ray acceleration in radiatively inefficient accretion flows
• Wave generation and heat flux suppression in astrophysical plasma systems
• Electron Heating in Low Mach Number Perpendicular shocks. I. Heating Mechanism
• Soft gamma rays from low accreting supermassive black holes and connection to energetic neutrinos
• Electron Heating in Low Mach Number Perpendicular shocks. II. Dependence on the Pre-Shock Conditions
• Production and persistence of extreme two-temperature plasmas in radiative relativistic turbulence
• Electron Heating by the Ion Cyclotron Instability in Collisionless Accretion Flows. II. Electron Heating Efficiency as a Function of Flow Conditions
• Ion versus electron heating in compressively driven astrophysical gyrokinetic turbulence
• Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*
• Combining timing characteristics with physical broadband spectral modelling of black hole X-ray binary GX~339$-$4
• Pressure-anisotropy-induced nonlinearities in the kinetic magnetorotational instability
• The Magnetohydrodynamic-Particle-In-Cell Module in Athena++: Implementation and Code Tests
• Synchrotron Firehose Instability
• Collisional behaviors of astrophysical collisionless plasmas
• Persistent mysteries of jet engines, formation, propagation, and particle acceleration: have they been addressed experimentally?
• Stochastic Ion Acceleration by the Ion-cyclotron Instability in a Growing Magnetic Field
• Features of collisionless turbulence in the intracluster medium from simulated Faraday rotation maps II: the effects of instabilities feedback
• Limits on the ions temperature anisotropy in turbulent intracluster medium
• Stochastic Electron Acceleration by Temperature Anisotropy Instabilities Under Solar Flare Plasma Conditions
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion