Electron heat flux instability

Saeed, Sundas; Sarfraz, M.; Yoon, Peter H.; Lazar, M.; Qureshi, M. N. S.

doi:10.1093/mnras/stw2900

Cited by 37 publications

(38 citation statements)

References 27 publications

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“…By doing so, we are able to separate the contribution of left-handed (LH) and RH circularly polarized modes. Thus, for ω > 0 we observe the RH contribution with positive and negative helicity, k > 0 and k < 0, respectively, see Saeed et al (2017a) for details. Most of the magnetic power is concentrated in the part with ω > 0 and k > 0, corresponding to the RH unstable modes with positive helicity, confirming the linear theory predictions (top panel) for a RH WHFI.…”

Section: Our Initial Setup Inmentioning

confidence: 74%

“…The quasi-stable states are expected in this case only for low drifts U b (or U c ), below the lower threshold (Gary et al 1999a;Shaaban et al 2018a) that seems to be confirmed by the observations (Gary et al 1999a;Gary et al 1999b;Tong et al 2018). Theoretically, whistlers may also satisfy resonance conditions with both electron populations, especially, for more energetic beams (U b > θ b ), but never develop, being heavily competed by the other faster growing modes, e.g., the electrostatic beam-plasma instabilities or the oblique instabilities (Gary & Saito 2007;Saito & Gary 2007a;Seough et al 2015;Saeed et al 2017a;Horaites et al 2018;Lee et al 2019;Vasko et al 2019;Verscharen et al 2019a). If the core electrons exhibit an important temperature anisotropy T c,⊥ > T c, the regime of WHFI may be significantly altered becoming specific to a standard whistler instability driven by temperature anisotropy, with lower thresholds and higher growth rates (Seough et al 2015;Shaaban et al 2018b).…”

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confidence: 99%

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Particle-in-cell Simulations of the Whistler Heat-flux Instability in Solar Wind Conditions

Lopez

Shaaban

Lazar

et al. 2019

ApJL

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In collision-poor plasmas from space, e.g., solar wind or stellar outflows, the heat-flux carried by the strahl or beaming electrons is expected to be regulated by the self-generated instabilities. Recently, simultaneous field and particle observations have indeed revealed enhanced whistler-like fluctuations in the presence of counter-beaming populations of electrons, connecting these fluctuations to the whistler heat-flux instability (WHFI). This instability is predicted only for limited conditions of electron beam-plasmas, and was not captured in numerical simulations yet. In this letter we report the first simulations of WHFI in particle-in-cell (PIC) setups, realistic for the solar wind conditions, and without temperature gradients or anisotropies to trigger the instability in the initiation phase. The velocity distributions have a complex reaction to the enhanced whistler fluctuations conditioning the instability saturation by a decrease of the relative drifts combined with induced (effective) temperature anisotropies (heating the core electrons and pitch-angle and energy scattering the strahl). These results are in good agreement with a recent quasilinear approach, and support therefore a largely accepted belief that WHFI saturates at moderate amplitudes. In anti-sunward direction the strahl becomes skewed with a pitch-angle distribution decreasing in width as electron energy increases, that seems to be characteristic to self-generated whistlers and not to small-scale turbulence.

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Section: Our Initial Setup Inmentioning

confidence: 74%

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confidence: 99%

Particle-in-cell Simulations of the Whistler Heat-flux Instability in Solar Wind Conditions

Lopez

Shaaban

Lazar

et al. 2019

ApJL

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“…The kinetic approach proposed in this paper enables an advanced characterization of the heat-flux instabilities for complex but realistic conditions, when the electron beams exhibit temperature anisotropies. The new unstable regimes uncovered here are controlled by two drivers, i.e., beaming velocity u b and beam anisotropy A b , and by the core plasma beta β c , and we have contrasted with idealized regimes of instabilities driven either by isotropic beams (Saeed et al, 2017a;Shaaban et al, 2018a) or by non-drifting (corebeam) populations with temperature anisotropies.…”

Section: Discussionmentioning

confidence: 99%

Beaming electromagnetic (or heat-flux) instabilities from the interplay with the electron temperature anisotropies

et al. 2018

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In space plasmas kinetic instabilities are driven by the beaming (drifting) components and/or the temperature anisotropy of charged particles. The heat-flux instabilities are known in the literature as electromagnetic modes destabilized by the electron beams (or strahls) aligned to the interplanetary magnetic field. A new kinetic approach is proposed here in order to provide a realistic characterization of heat-flux instabilities under the influence of electrons with temperature anisotropy. Numerical analysis is based on the kinetic Vlasov-Maxwell theory for two electron counter-streaming (core and beam) populations with temperature anisotropies, and stationary, isotropic protons. The main properties of electromagnetic heat-flux instabilities are found to be markedly changed by the temperature anisotropy of electron beam A b = T ⊥ /T = 1, leading to stimulation of either the whistler branch if A b > 1, or the firehose branch for A b < 1. For a high temperature anisotropy whistlers switch from heat-flux to a standard regime, when their instability is inhibited by the beam.

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“…Non‐Maxwellian‐like distributions are ubiquitous as reported in different observational findings (Maksimovic et al, ; Štverák et al, ). One can model energetic halo electrons with kappa distributions to see its effects in dispersion analysis following earlier works of Lazar, Poedts, and Schlickeiser (), Lazar et al (), and Saeed, Sarfraz, et al (). In this regard, our present study can be taken as an important step toward global thinking of modeling the solar wind plasma.…”

Section: Summary and Discussionmentioning

confidence: 99%

A Moment‐Based Quasilinear Theory for Electron Firehose Instability Driven by Solar Wind Core/Halo Electrons

Sarfraz

2018

JGR Space Physics

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In dilute space plasmas, especially in the solar wind, the microinstabilities are regarded as a major candidate to regulate the unchecked rise in temperature anisotropy near Earth orbit. The present paper considers parallel electron firehose mode, which is driven unstable under the condition of excessive electron temperature along the ambient magnetic field, that is, T∥e>T⊥e. The present study assumes bi‐Maxwellian model of solar wind species comprising ions, core, and halo electron components and, in addition, allowing their temperatures to evolve in time t. Employing the macroscopic quasilinear method, a set of equations has been constructed whose solutions give a dynamical picture of the modification in initial particles distributions and wave energy density associated with unstable electron firehose mode. The present scheme, further, confirms the marginal stability curves corresponding to ions, core, and halo electrons, separately. As we dynamically couple solar wind electrons with ions to determine the dynamics of instability, it may amount a further step toward global kinetic solar wind modeling.

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Electron heat flux instability

Cited by 37 publications

References 27 publications

Particle-in-cell Simulations of the Whistler Heat-flux Instability in Solar Wind Conditions

Particle-in-cell Simulations of the Whistler Heat-flux Instability in Solar Wind Conditions

Beaming electromagnetic (or heat-flux) instabilities from the interplay with the electron temperature anisotropies

A Moment‐Based Quasilinear Theory for Electron Firehose Instability Driven by Solar Wind Core/Halo Electrons

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