The Evolution of the Electron Number Density in the Coma of Comet 67P at the Location of Rosetta from 2015 November through 2016 March

A comet ionospheric model assuming the plasma moves radially outward with the same bulk speed as the neutral gas and not being subject to severe reduction through dissociative recombination has previously been tested in a series of case studies associated with the Rosetta mission at comet 67P/Churyu...

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Bibliographic Details
Published in:The Astrophysical journal 2019-08, Vol.881 (1), p.6
Main Authors: Vigren, E., Edberg, N. J. T., Eriksson, A. I., Galand, M., Henri, P., Johansson, F. L., Odelstad, E., Rubin, M., Valliéres, X.
Format: Article
Language:English
Subjects:
Astrophysics
Case studies
Comet heads
Comet nuclei
comets: individual (67P)
Consortia
Earth and Planetary Astrophysics
Electrons
Impedance probes
Ionization
Ionospheric models
molecular processes
Mutual impedance
Neutral gases
Perihelions
Photoionization
Physics
Pressure sensors
Rosetta mission
Space Physics
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Summary:A comet ionospheric model assuming the plasma moves radially outward with the same bulk speed as the neutral gas and not being subject to severe reduction through dissociative recombination has previously been tested in a series of case studies associated with the Rosetta mission at comet 67P/Churyumov-Gerasimenko. It has been found that at low activity and within several tens of kilometers from the nucleus such models (which originally were developed for such conditions) generally work well in reproducing observed electron number densities, in particular when plasma production through both photoionization and electron-impact ionization is taken into account. Near perihelion, case studies have, on the contrary, shown that applying similar assumptions overestimates the observed electron number densities at the location of Rosetta. Here we compare Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Comet Pressure sensor-driven model results with Rosetta Plasma Consortium/Mutual Impedance Probe-derived electron number densities for an extended time period (2015 November through 2016 March) during the postperihelion phase with southern summer/spring. We observe a gradual transition from a state when the model grossly overestimates (by more than a factor of 10) the observations to being in reasonable agreement during 2016 March.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.3847/1538-4357/ab29f7