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Electron dynamics near diamagnetic regions of comet 67P/Churyumov- Gerasimenko

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Title: Electron dynamics near diamagnetic regions of comet 67P/Churyumov- Gerasimenko
Authors: Madanian, H
Burch, JL
Eriksson, AI
Cravens, TE
Galand, M
Vigren, E
Goldstein, R
Nemeth, Z
Mokashi, P
Richter, I
Rubin, M
Item Type: Journal Article
Abstract: The Rosetta spacecraft detected transient and sporadic diamagnetic regions around comet 67P/Churyumov-Gerasimenko. In this paper we present a statistical analysis of bulk and suprathermal electron dynamics, as well as a case study of suprathermal electron pitch angle distributions (PADs) near a diamagnetic region. Bulk electron densities are correlated with the local neutral density and we find a distinct enhancement in electron densities measured over the southern latitudes of the comet. Flux of suprathermal electrons with energies between tens of eV to a couple of hundred eV decreases each time the spacecraft enters a diamagnetic region. We propose a mechanism in which this reduction can be explained by solar wind electrons that are tied to the magnetic field and after having been transported adiabatically in a decaying magnetic field environment, have limited access to the diamagnetic regions. Our analysis shows that suprathermal electron PADs evolve from an almost isotropic outside the diamagnetic cavity to a field-aligned distribution near the boundary. Electron transport becomes chaotic and non-adiabatic when electron gyroradius becomes comparable to the size of the magnetic field line curvature, which determines the upper energy limit of the flux variation. This study is based on Rosetta observations at around 200 ​km cometocentric distance when the comet was at 1.24 AU from the Sun and during the southern summer cometary season.
Issue Date: 1-Aug-2020
Date of Acceptance: 30-Mar-2020
URI: http://hdl.handle.net/10044/1/80465
DOI: 10.1016/j.pss.2020.104924
ISSN: 0032-0633
Publisher: Elsevier BV
Journal / Book Title: Planetary and Space Science
Volume: 187
Copyright Statement: © 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor/Funder: European Space Agency / Estec
European Space Agency / Estec
Funder's Grant Number: 4000119035/16/ES/JD
4000119035/16/ES/JD
Keywords: Science & Technology
Physical Sciences
Astronomy & Astrophysics
Comet 67P/Churyumov-Gerasimenko
Rosetta
Plasma dynamics
Diamagnetic cavity
ION COMPOSITION
PLASMA
RPC
EVOLUTION
CAVITY
MAGNETOMETER
ENVIRONMENT
PROBE
67P
0201 Astronomical and Space Sciences
Astronomy & Astrophysics
Publication Status: Published
Article Number: ARTN 104924
Online Publication Date: 2020-04-19
Appears in Collections:Space and Atmospheric Physics
Physics