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

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This publication is imported from Aalto University research portal.
View publication in the Research portal
View/Open full text file from the Research portal
Degree programme
Monthly Notices of the Royal Astronomical Society, Volume 469, issue Suppl
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.
plasmas, methods: data analysis, comets: individual: 67P
Other note
Nilsson , H , Wieser , G S , Behar , E , Gunell , H , Wieser , M , Galand , M , Simon Wedlund , C , Alho , M , Goetz , C , Yamauchi , M , Henri , P , Odelstad , E & Vigren , E 2017 , ' Evolution of the ion environment of comet 67P during the Rosetta mission as seen by RPC-ICA ' , Monthly Notices of the Royal Astronomical Society , vol. 469 , no. Suppl , pp. S252–S261 . https://doi.org/10.1093/mnras/stx1491