Evolution of the ion environment of comet 67P during the Rosetta mission as seen by RPC-ICA

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Title: Evolution of the ion environment of comet 67P during the Rosetta mission as seen by RPC-ICA
Authors: Nilsson, H
Wieser, GS
Behar, E
Gunell, H
Wieser, M
Galand, M
Simon Wedlund, C
Alho, M
Goetz, C
Yamauchi, M
Henri, P
Odelstad, E
Vigren, E
Item Type: Journal Article
Abstract: Rosetta has followed comet 67P from low activity at more than 3.6 au heliocentric distance to high activity at perihelion (1.24 au) and then out again. We provide a general overview of the evolution of the dynamic ion environment using data from the RPC-ICA ion spectrometer. We discuss where Rosetta was located within the evolving comet magnetosphere. For the initial observations, the solar wind permeated all of the coma. In 2015 mid-April, the solar wind started to disappear from the observation region, to re-appear again in 2015 December. Low-energy cometary ions were seen at first when Rosetta was about 100 km from the nucleus at 3.6 au, and soon after consistently throughout the mission except during the excursions to farther distances from the comet. The observed flux of low-energy ions was relatively constant due to Rosetta's orbit changing with comet activity. Accelerated cometary ions, moving mainly in the antisunward direction gradually became more common as comet activity increased. These accelerated cometary ions kept being observed also after the solar wind disappeared from the location of Rosetta, with somewhat higher fluxes further away from the nucleus. Around perihelion, when Rosetta was relatively deep within the comet magnetosphere, the fluxes of accelerated cometary ions decreased, as did their maximum energy. The disappearance of more energetic cometary ions at close distance during high activity is suggested to be due to a flow pattern where these ions flow around the obstacle of the denser coma or due to charge exchange losses.
Issue Date: 21-Jun-2017
Date of Acceptance: 12-Jun-2017
URI: http://hdl.handle.net/10044/1/56684
DOI: https://dx.doi.org/10.1093/mnras/stx1491
ISSN: 0035-8711
Publisher: Oxford Univesity Press
Start Page: S252
End Page: S261
Journal / Book Title: Monthly Notices of the Royal Astronomical Society
Volume: 469
Issue: Suppl_2
Copyright Statement: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Sponsor/Funder: Imperial College Trust
Science and Technology Facilities Council (STFC)
European Space Agency / Estec
Funder's Grant Number: N/A
ST/N000692/1
4000119035/16/ES/JD
Keywords: 0201 Astronomical And Space Sciences
Astronomy & Astrophysics
Publication Status: Published
Appears in Collections:Space and Atmospheric Physics
Physics
Faculty of Natural Sciences



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