Particle-in-cell Simulations of the Whistler Heat-flux Instability in Solar Wind Conditions
| Autor: | Stefaan Poedts, Peter H. Yoon, Shaaban Mohammed Shaaban Shaaban, Giovanni Lapenta, Rodrigo A. López, Alfredo Micera, Marian Lazar |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
010504 meteorology & atmospheric sciences
Whistler FOS: Physical sciences Interplanetary medium Electron Astronomy & Astrophysics 01 natural sciences Instability Article Physics - Space Physics Core electron 0103 physical sciences waves 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences Physics Science & Technology Astronomy and Astrophysics numerical [methods] plasmas Physics - Plasma Physics Space Physics (physics.space-ph) Computational physics ELECTRONS Plasma Physics (physics.plasm-ph) Solar wind Strahl Astrophysics - Solar and Stellar Astrophysics Heat flux solar wind Space and Planetary Science instabilities Physics::Space Physics Physical Sciences HALO interplanetary medium |
| Popis: | 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. Comment: Accepted for publication in ApJL |
| Databáze: | OpenAIRE |
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