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Indirect Observations of Electric Fields at Comet 67P
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  • Anja Moeslinger,
  • Hans Nilsson,
  • Gabriella Stenberg Wieser,
  • Herbert Gunell,
  • Charlotte Goetz
Anja Moeslinger
Swedish Institute of Space Physics

Corresponding Author:anja.moeslinger@irf.se

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Hans Nilsson
Swedish Institute of Space Physics
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Gabriella Stenberg Wieser
Swedish Institute of Space Physics
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Herbert Gunell
UmeƄ University
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Charlotte Goetz
Northumbria University
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Abstract

No spacecraft visiting a comet has been equipped with instruments to directly measure the static electric field. However, the electric field can occasionally be estimated indirectly by observing its effects on the ion velocity distribution. We present such observations made by the Rosetta spacecraft on 19th of April 2016 when comet 67P was at a low outgassing rate and the plasma environment was relatively homogeneous. The ion velocity distributions show the cometary ions on the first half of their gyration. We estimate the bulk drift velocity and the gyration speed from the distributions. By using the local measured magnetic field and assuming an E x B drift of the gyrocentre, we get an estimate for the average electric field driving this ion motion. We analyse a period of 13h, during which the plasma environment does not change drastically. We find that the average strength of the electric field is 0.21mV/m. The direction of the electric field is mostly anti-sunward. This is in agreement with previous results based on different methods
09 Jun 2023Submitted to ESS Open Archive
11 Jun 2023Published in ESS Open Archive