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A collisional test particle model of electrons at a comet

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Title: A collisional test particle model of electrons at a comet
Authors: Stephenson, P
Galand, M
Deca, J
Henri, P
Carnielli, G
Item Type: Journal Article
Abstract: We have developed the first 3D collisional model of electrons at a comet, which we use to examine the impact of electron-neutral collisions in the weakly outgassing regime. The test-particle Monte Carlo model uses electric and magnetic fields from a fully kinetic Particle-in-Cell (PiC) model as an input. In our model, electrons originate from the solar wind or from ionization of the neutral coma, either by electron impact or absorption of an extreme ultraviolet photon. All relevant electron-neutral collision processes are included in the model including elastic scattering, excitation, and ionization. Trajectories of electrons are validated against analytically known drifts and the stochastic energy degradation used in the model is compared to the continuous slowing down approximation. Macroscopic properties of the solar wind and cometary electron populations, such as density and temperature, are validated with simple known cases and via comparison with the collisionless PiC model. We demonstrate that electrons are trapped close to the nucleus by the ambipolar electric field, causing an increase in the efficiency of electron-neutral collisions. Even at a low-outgassing rate (Q = 1026 s−1), electron-neutral collisions are shown to cause significant cooling in the coma. The model also provides a multistep numerical framework that is used to assess the influence of the electron-to-ion mass ratio, enabling access to electron dynamics with a physical electron mass.
Issue Date: 1-Apr-2022
Date of Acceptance: 14-Dec-2021
URI: http://hdl.handle.net/10044/1/94174
DOI: 10.1093/mnras/stac055
ISSN: 0035-8711
Publisher: Royal Astronomical Society
Start Page: 4090
End Page: 4108
Journal / Book Title: Monthly Notices of the Royal Astronomical Society
Volume: 511
Issue: 3
Copyright Statement: © 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited
Keywords: Science & Technology
Physical Sciences
Astronomy & Astrophysics
comets: general
comets: individual: 67P/CG
SUPRATHERMAL ELECTRONS
ENERGY DEPOSITION
PLASMA
ROSETTA
RPC
WATER
67P/CHURYUMOV-GERASIMENKO
PRECIPITATION
IONOSPHERE
EXCITATION
Astronomy & Astrophysics
0201 Astronomical and Space Sciences
Publication Status: Published
Online Publication Date: 2022-02-07
Appears in Collections:Space and Atmospheric Physics
Physics
Faculty of Natural Sciences



This item is licensed under a Creative Commons License Creative Commons