uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
A 1D Model of Radial Ion Motion Interrupted by Ion-Neutral Interactions in a Cometary Coma
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
2017 (English)In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 153, no 4, 150Article in journal (Refereed) Published
Abstract [en]

Because ion- neutral reaction cross sections are energy dependent, the distance from a cometary nucleus within which ions remain collisionally coupled to the neutrals is dictated not only by the comet's activity level but also by the electromagnetic fields in the coma. Here we present a 1D model simulating the outward radial motion of water group ions with radial acceleration by an ambipolar electric field interrupted primarily by charge transfer processes with H2O. We also discuss the impact of plasma waves. For a given electric field profile, the model calculates key parameters, including the total ion density, n(I), the H3O+/H2O+ number density and flux ratios, R-dens and R-flux, and the mean ion drift speed, < u(I)>, as a function of cometocentric distance. We focus primarily on a coma roughly resembling that of the ESA Rosetta mission target comet 67P/Churyumov-Gerasimenko near its perihelion in 2015 August. In the presence of a weak ambipolar electric field in the radial direction the model results suggest that the neutral coma is not sufficiently dense to keep the mean ion flow speed close to that of the neutrals by the spacecraft location (similar to 200 km from the nucleus). In addition, for electric field profiles giving nI and < u(I)> within limits constrained by measurements, the Rdens values are significantly higher than values typically observed. However, when including the ion motion in large-amplitude plasma waves in the model, results more compatible with observations are obtained. We suggest that the variable and often low H3O+/H2O+ number density ratios observed may reflect nonradial ion trajectories strongly influenced by electromagnetic forces and/or plasma instabilities, with energization of the ion population by plasma waves.

Place, publisher, year, edition, pages
2017. Vol. 153, no 4, 150
Keyword [en]
comets: individual (67P), molecular processes
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-321331DOI: 10.3847/1538-3881/aa6006ISI: 000397525300004OAI: oai:DiVA.org:uu-321331DiVA: diva2:1103980
Funder
Swedish National Space Board
Available from: 2017-05-31 Created: 2017-05-31 Last updated: 2017-05-31Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Vigren, ErikEriksson, Anders I.

Search in DiVA

By author/editor
Vigren, ErikEriksson, Anders I.
By organisation
Swedish Institute of Space Physics, Uppsala Division
In the same journal
Astronomical Journal
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 155 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf