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Impact of a cometary outburst on its ionosphere Rosetta Plasma Consortium observations of the outburst exhibited by comet 67P/Churyumov-Gerasimenko on 19 February 2016
CNRS, LPC2E, Orleans, France..
CNRS, LPC2E, Orleans, France..
CNRS, LPC2E, Orleans, France..
Imperial Coll, South Kensington Campus, London SW7 2AZ, England..
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2017 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 607, article id A34Article in journal (Refereed) Published
Abstract [en]

We present a detailed study of the cometary ionospheric response to a cometary brightness outburst using in situ measurements for the first time. The comet 67P/Churyumov-Gerasimenko (67P) at a heliocentric distance of 2.4 AU from the Sun, exhibited an outburst at similar to 1000 UT on 19 February 2016, characterized by an increase in the coma surface brightness of two orders of magnitude. The Rosetta spacecraft monitored the plasma environment of 67P from a distance of 30 km, orbiting with a relative speed of similar to 0.2 m s(-1). The onset of the outburst was preceded by pre-outburst decreases in neutral gas density at Rosetta, in local plasma density, and in negative spacecraft potential at similar to 0950 UT. In response to the outburst, the neutral density increased by a factor of similar to 1.8 and the local plasma density increased by a factor of similar to 3, driving the spacecraft potential more negative. The energetic electrons (tens of eV) exhibited decreases in the flux of factors of similar to 2 to 9, depending on the energy of the electrons. The local magnetic field exhibited a slight increase in amplitude (similar to 5 nT) and an abrupt rotation (similar to 36.4 degrees) in response to the outburst. A weakening of 10-100 mHz magnetic field fluctuations was also noted during the outburst, suggesting alteration of the origin of the wave activity by the outburst. The plasma and magnetic field effects lasted for about 4 h, from similar to 1000 UT to 1400 UT. The plasma densities are compared with an ionospheric model. This shows that while photoionization is the main source of electrons, electron-impact ionization and a reduction in the ion outflow velocity need to be accounted for in order to explain the plasma density enhancement near the outburst peak.

Place, publisher, year, edition, pages
2017. Vol. 607, article id A34
Keywords [en]
plasmas, waves, methods: data analysis, methods: observational, comets: general, comets: individual: 67P/Churyumov-Gerasimenko
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-340902DOI: 10.1051/0004-6361/201730591ISI: 000414474000003OAI: oai:DiVA.org:uu-340902DiVA, id: diva2:1180679
Available from: 2018-02-06 Created: 2018-02-06 Last updated: 2018-03-13Bibliographically approved

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Eriksson, Anders I.Odelstad, EliasEdberg, Niklas J. T.

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Swedish Institute of Space Physics, Uppsala DivisionDepartment of Physics and Astronomy
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Astronomy, Astrophysics and Cosmology

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