Birth of a comet magnetosphere: A spring of water ions

Hans Nilsson (1) , G. Stenberg Wieser (1) , E. Behar (1) , C. S. Wedlund , H. Gunell (2) , M. Yamauchi (1) , R. Lundin (1) , S. Barabash (1) , M. Wieser (1) , C. Carr (3) , Emanuele Cupido (3) , James L. Burch (4) , A. Fedorov (5) , J.-A. Sauvaud (5) , H. Koskinen (6) , E. Kallio (7) , Jean-Pierre Lebreton (8) , A. Eriksson , N. Edberg (9) , Raymond Goldstein (10) , Pierre Henri (8) , Christoph Koenders (11) , Pat Mokashi (10) , Zoltán Nemeth (12) , Ingo Richter (11) , K. Szego (12) , M. Volwerk (13) , C. Vallat (14) , M. Rubin (15)

1 IRF - Swedish Institute of Space Physics [Uppsala]
2 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique
3 Blackett Laboratory
4 Space Science Division [San Antonio]
5 IRAP - Institut de recherche en astrophysique et planétologie
6 FMI - Finnish Meteorological Institute
7 School of Electrical Engineering [Aalto Univ]
8 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
9 IRF - Swedish Institute of Space Physics [Kiruna]
10 SwRI - Southwest Research Institute [San Antonio]
11 Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig]
12 Wigner Research Centre for Physics [Budapest]
13 OeAW - Austrian Academy of Sciences
14 Rosetta Science Ground Segment
15 Physikalisches Institut [Bern]

The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (similar to 3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (<800 electron volts), produced upstream of Rosetta, and lower energy locally produced ions; we estimate the fluxes of both ion species and energetic neutral atoms.

Domains: Astrophysics [astro-ph]

Hans Nilsson, G. Stenberg Wieser, E. Behar, C. S. Wedlund, H. Gunell, et al.. Birth of a comet magnetosphere: A spring of water ions. Science, 2015, 347 (6220), pp.aaa0571. ⟨10.1126/science.aaa0571⟩. ⟨insu-01256291⟩