Mach number dependence of electron heating in high Mach number quasiperpendicular shocks

Matsukiyo, Shuichi

doi:10.1063/1.3372137

Cited by 23 publications

(21 citation statements)

References 45 publications

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“…To understand electron heating in collisionless shocks, fully-kinetic simulations with the particle-incell (PIC) method (Birdsall & Langdon 1991;Hockney & Eastwood 1981) are essential to self-consistently capture the role of electron and proton plasma instabilities in particle heating. So far, most PIC studies of electron heating in shocks have focused on the regime of high sonic Mach number (M s 10, where M s is the ratio of the upstream flow speed relative to the shock to the upstream sound speed) and low plasma beta (β p0 1, where β p0 is the ratio of thermal and magnetic pressures) appropriate for supernova remnants (Dieckmann et al 2012;Matsukiyo & Scholer 2003;Matsukiyo 2010). In the first paper of this series (Guo et al 2017, hereafter, Paper I), we investigated by means of analytical theory and two-dimensional (2D) PIC simulations the physics of electron heating in low Mach number perpendicular shocks, a regime so far unexplored.…”

Section: Introductionmentioning

confidence: 99%

Electron Heating in Low Mach Number Perpendicular Shocks. II. Dependence on the Pre-shock Conditions

Guo

Sironi

Narayan

2018

ApJ

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Recent X-ray observations of merger shocks in galaxy clusters have shown that the post-shock plasma is two-temperature, with the protons being hotter than the electrons. In this work, the second of a series, we investigate by means of two-dimensional particle-in-cell simulations the efficiency of electron irreversible heating in perpendicular low Mach number shocks. We consider values of plasma beta (ratio of thermal and magnetic pressures) in the range 4 β p0 32 and sonic Mach number (ratio of shock speed to pre-shock sound speed) in the range 2 M s 5, as appropriate for galaxy cluster shocks. As shown in Paper I, magnetic field amplification -induced by shock compression of the preshock field, or by strong proton cyclotron and mirror modes accompanying the relaxation of proton temperature anisotropy -can drive the electron temperature anisotropy beyond the threshold of the electron whistler instability. The growth of whistler waves breaks the electron adiabatic invariance, and allows for efficient entropy production. We find that the post-shock electron temperature T e2 exceeds the adiabatic expectation T e2,ad by an amount (T e2 − T e2,ad )/T e0 0.044 M s (M s − 1) (here, T e0 is the pre-shock temperature), which depends only weakly on the plasma beta, over the range 4 β p0 32 which we have explored, and on the proton-to-electron mass ratio (the coefficient of 0.044 is measured for our fiducial m i /m e = 49, and we estimate that it will decrease to 0.03 for the realistic mass ratio). Our results have important implications for current and future observations of galaxy cluster shocks in the radio band (synchrotron emission and Sunyaev-Zel'dovich effect) and at X-ray frequencies.

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Section: Introductionmentioning

confidence: 99%

Electron Heating in Low Mach Number Perpendicular Shocks. II. Dependence on the Pre-shock Conditions

Guo

Sironi

Narayan

2018

ApJ

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“…When the relative velocity between incoming electrons and incoming/reflected ions becomes slower than the electron thermal velocity at lowerMach-number perpendicular shocks, high-frequency electrostatic waves are not excited due to the damping by thermal electrons, and the modified two-stream instability (MTSI) [12][13][14][15][16] becomes dominant. Then, obliquely propagating electromagnetic whistler mode waves are excited at a frequency between the electron cyclotron frequency and the lower hybrid resonance frequency 5,6,[17][18][19][20][21] . Our previous study 22 has clearly shown that for a relatively low Mach number (M A = 6) perpendicular shock the MTSI becomes dominant with higher mass ratios (m i /m e ≥ 100) while the ECDI becomes dominant with smaller mass ratio (m i /m e = 25).…”

Section: Introductionmentioning

confidence: 99%

Dynamics and microinstabilities at perpendicular collisionless shock: A comparison of large-scale two-dimensional full particle simulations with different ion to electron mass ratio

Umeda¹,

Kidani²,

Matsukiyo³

et al. 2014

Physics of Plasmas

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Large-scale two-dimensional (2D) full particle-in-cell simulations are carried out for studying the relationship between the dynamics of a perpendicular shock and microinstabilities generated at the shock foot. The structure and dynamics of collisionless shocks are generally determined by Alfven Mach number and plasma beta, while microinstabilities at the shock foot are controlled by the ratio of the upstream bulk velocity to the electron thermal velocity and the ratio of the plasma-to-cyclotron frequency. With a fixed Alfven Mach number and plasma beta, the ratio of the upstream bulk velocity to the electron thermal velocity is given as a function of the ion-to-electron mass ratio. The present 2D full PIC simulations with a relatively low Alfven Mach number (M A ∼ 6) show that the modified two-stream instability is dominant with higher ion-to-electron mass ratios. It is also confirmed that waves propagating downstream are more enhanced at the shock foot near the shock ramp as the mass ratio becomes higher. The result suggests that these waves play a role in the modification of the dynamics of collisionless shocks through the interaction with shock front ripples.

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“…Guo et al (2018) carried out two-dimensional kinetic particle-in-cell simulations of low-Mach-number shocks, assuming galactic shocks, and showed T e /T i ∼ 0.24 at M = 5, independent of the plasma beta ranging 4 < β < 32. In addition, Matsukiyo (2010) found that the post-shock temperature ratio is proportional to the magnetosonic Mach number and T e /T i = 0.01 when the shock parameters are β = 10 and M = 14.…”

Section: Electron Heating At Shock Wavesmentioning

confidence: 98%

Two-temperature magnetohydrodynamic simulations for sub-relativistic active galactic nucleus jets: dependence on the fraction of the electron heating

Ohmura

Machida

Nakamura

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present the results of two-temperature magnetohydrodynamic simulations of the propagation of sub-relativistic jets of active galactic nuclei. The dependence of the electron and ion temperature distributions on the fraction of electron heating f e at the shock front is studied for f e = 0, 0.05, and 0.2. Numerical results indicate that in sub-relativistic, rarefied jets, the jet plasma crossing the terminal shock forms a hot, two-temperature plasma in which the ion temperature is higher than the electron temperature. The two-temperature plasma expands and forms a backflow referred to as a cocoon, in which the ion temperature remains higher than the electron temperature for longer than 100 Myr. Electrons in the cocoon are continuously heated by ions through Coulomb collisions, and the electron temperature thus remains at T e > 10 9 K in the cocoon. X-ray emissions from the cocoon are weak because the electron number density is low. Meanwhile, soft X-rays are emitted from the shocked intracluster medium surrounding the cocoon. Mixing of the jet plasma and the shocked intracluster medium through the Kelvin-Helmholtz instability at the interface enhances X-ray emissions around the contact discontinuity between the cocoon and shocked intracluster medium.

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Mach number dependence of electron heating in high Mach number quasiperpendicular shocks

Cited by 23 publications

References 45 publications

Electron Heating in Low Mach Number Perpendicular Shocks. II. Dependence on the Pre-shock Conditions

Electron Heating in Low Mach Number Perpendicular Shocks. II. Dependence on the Pre-shock Conditions

Dynamics and microinstabilities at perpendicular collisionless shock: A comparison of large-scale two-dimensional full particle simulations with different ion to electron mass ratio

Two-temperature magnetohydrodynamic simulations for sub-relativistic active galactic nucleus jets: dependence on the fraction of the electron heating

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