Rights statement: This is an author-created, un-copyedited version of an article accepted for publication/published in Astrophysical Journal Letters. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi: 10.3847/2041-8213/abc0e8
Accepted author manuscript, 1.95 MB, PDF document
Available under license: CC BY-NC: Creative Commons Attribution-NonCommercial 4.0 International License
Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Particle-in-cell Simulation of Whistler Heat-flux Instabilities in the Solar Wind : Heat-flux Regulation and Electron Halo Formation. / Micera, A.; Zhukov, A.N.; López, R.A. et al.
In: Astrophysical Journal Letters, Vol. 903, No. 1, L23, 02.11.2020.Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Particle-in-cell Simulation of Whistler Heat-flux Instabilities in the Solar Wind
T2 - Heat-flux Regulation and Electron Halo Formation
AU - Micera, A.
AU - Zhukov, A.N.
AU - López, R.A.
AU - Innocenti, M.E.
AU - Lazar, M.
AU - Boella, E.
AU - Lapenta, G.
N1 - This is an author-created, un-copyedited version of an article accepted for publication/published in Astrophysical Journal Letters. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi: 10.3847/2041-8213/abc0e8
PY - 2020/11/2
Y1 - 2020/11/2
N2 - We present results of a two-dimensional fully kinetic particle-in-cell simulation in order to shed light on the role of whistler waves in the scattering of strahl electrons and in the heat-flux regulation in the solar wind. We model the electron velocity distribution function as initially composed of core and strahl populations as typically encountered in the near-Sun solar wind as observed by Parker Solar Probe. We demonstrate that, as a consequence of the evolution of the electron velocity distribution function (VDF), two branches of the whistler heat-flux instability can be excited, which can drive whistler waves propagating in the direction oblique or parallel to the background magnetic field. First, oblique whistler waves induce pitch-angle scattering of strahl electrons, toward higher perpendicular velocities. This leads to the broadening of the strahl pitch-angle distribution and hence to the formation of a halo-like population at the expense of the strahl. Later on, the electron VDF experiences the effect of parallel whistler waves, which contributes to the redistribution of the particles scattered in the perpendicular direction into a more symmetric halo, in agreement with observations. Simulation results show a remarkable agreement with the linear theory of the oblique whistler heat-flux instability. The process is accompanied by a significant decrease of the heat flux carried by the strahl population.
AB - We present results of a two-dimensional fully kinetic particle-in-cell simulation in order to shed light on the role of whistler waves in the scattering of strahl electrons and in the heat-flux regulation in the solar wind. We model the electron velocity distribution function as initially composed of core and strahl populations as typically encountered in the near-Sun solar wind as observed by Parker Solar Probe. We demonstrate that, as a consequence of the evolution of the electron velocity distribution function (VDF), two branches of the whistler heat-flux instability can be excited, which can drive whistler waves propagating in the direction oblique or parallel to the background magnetic field. First, oblique whistler waves induce pitch-angle scattering of strahl electrons, toward higher perpendicular velocities. This leads to the broadening of the strahl pitch-angle distribution and hence to the formation of a halo-like population at the expense of the strahl. Later on, the electron VDF experiences the effect of parallel whistler waves, which contributes to the redistribution of the particles scattered in the perpendicular direction into a more symmetric halo, in agreement with observations. Simulation results show a remarkable agreement with the linear theory of the oblique whistler heat-flux instability. The process is accompanied by a significant decrease of the heat flux carried by the strahl population.
U2 - 10.3847/2041-8213/abc0e8
DO - 10.3847/2041-8213/abc0e8
M3 - Journal article
VL - 903
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
SN - 2041-8205
IS - 1
M1 - L23
ER -