Model-observation comparisons of electron number densities in the coma of 67P/Churyumov–Gerasimenko during 2015 January

Vigren, E.; Altwegg, Kathrin; Edberg, N. J. T.; Eriksson, A. I.; Galand, M.; Henri, P.; Johansson, F.; Odelstad, E.; Tzou, Chia-Yu; Valliéres, X. (2016). Model-observation comparisons of electron number densities in the coma of 67P/Churyumov–Gerasimenko during 2015 January. Astronomical journal, 152(3), p. 59. University of Chicago Press 10.3847/0004-6256/152/3/59

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During 2015 January 9–11, at a heliocentric distance of ~2.58–2.57 au, the ESA Rosetta spacecraft resided at a cometocentric distance of ~28 km from the nucleus of comet 67P/Churyumov–Gerasimenko, sweeping the terminator at northern latitudes of 43°N–58°N. Measurements by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Comet Pressure Sensor (ROSINA/COPS) provided neutral number densities. We have computed modeled electron number densities using the neutral number densities as input into a Field Free Chemistry Free model, assuming H2O dominance and ion-electron pair formation by photoionization only. A good agreement (typically within 25%) is found between the modeled electron number densities and those observed from measurements by the Mutual Impedance Probe (RPC/MIP) and the Langmuir Probe (RPC/LAP), both being subsystems of the Rosetta Plasma Consortium. This indicates that ions along the nucleus-spacecraft line were strongly coupled to the neutrals, moving radially outward with about the same speed. Such a statement, we propose, can be further tested by observations of H3O+/H2O+ number density ratios and associated comparisons with model results.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Altwegg, Kathrin and Tzou, Chia-Yu


500 Science > 520 Astronomy
600 Technology > 620 Engineering
500 Science > 530 Physics




University of Chicago Press




Katharina Weyeneth-Moser

Date Deposited:

13 Jul 2017 16:25

Last Modified:

13 Jul 2017 16:25

Publisher DOI:





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