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Updated: Apr 18, 2026

Scattering And Absorption of Light in Planetary Regoliths
Published on: July 1, 2019
Cometary science. Birth of a comet magnetosphere: a spring of water ions
Hans Nilsson1, Gabriella Stenberg Wieser2, Etienne Behar3
1Swedish Institute of Space Physics, Post Office Box 812, 981 28 Kiruna, Sweden. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Rymdcampus 1, 981 28 Kiruna, Sweden. hans.nilsson@irf.se.
Abstract:
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 (~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.
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