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Suprathermal Electr...
Suprathermal Electrons In Titan's Sunlit Ionosphere Model-Observation Comparisons
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Vigren, Erik (author)
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Galand, M. (author)
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Wellbrock, A. (author)
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Coates, A. J. (author)
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Cui, J. (author)
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Edberg, Niklas J. T. (author)
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Lavvas, P. (author)
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Sagnieres, L. (author)
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Snowden, D. (author)
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Vuitton, V. (author)
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Wahlund, Jan-Erik (author)
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(publisher)
- 2016
- 2016
- English.
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In: Astrophysical Journal. - 0004-637X. ; 826:2
Abstract
Subject headings
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- The dayside ionosphere of the Saturnian satellite Titan is generated mainly from photoionization of N-2 and CH4. We compare model-derived suprathermal electron intensities with spectra measured by the Cassini Plasma Spectrometer/Electron Spectrometer (CAPS/ELS) in Titan's sunlit ionosphere (altitudes of 970-1250 km) focusing on the T40, T41, T42, and T48 Titan flybys by the Cassini spacecraft. The model accounts only for photoelectrons and associated secondary electrons, with a main input being the impinging solar EUV spectra as measured by the Thermosphere Ionosphere Mesosphere Energy and Dynamics/Solar EUV Experiment and extrapolated to Saturn. Associated electron-impact electron production rates have been derived from ambient number densities of N-2 and CH4 (measured by the Ion Neutral Mass Spectrometer/Closed Source Neutral mode) and related energy-dependent electron-impact ionization cross sections. When integrating up to electron energies of 60 eV, covering the bulk of the photoelectrons, the model-based values exceed the observationally based values typically by factors of similar to 3 +/- 1. This finding is possibly related to current difficulties in accurately reproducing the observed electron number densities in Titan's dayside ionosphere. We compare the utilized dayside CAPS/ELS spectra with ones measured in Titan's nightside ionosphere during the T55-T59 flybys. The investigated nightside locations were associated with higher fluxes of high-energy (>100 eV) electrons than the dayside locations. As expected, for similar neutral number densities, electrons with energies <60 eV give a higher relative contribution to the total electron-impact ionization rates on the dayside (due to the contribution from photoelectrons) than on the nightside.
Subject headings
- Natural Sciences (hsv)
- Physical Sciences (hsv)
- Astronomy, Astrophysics and Cosmology (hsv)
- Naturvetenskap (hsv)
- Fysik (hsv)
- Astronomi, astrofysik och kosmologi (hsv)
Keyword
- molecular processes
- planets and satellites: individual (Titan)
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- By the author/editor
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Vigren, Erik
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Galand, M.
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Wellbrock, A.
-
Coates, A. J.
-
Cui, J.
-
Edberg, Niklas J ...
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show more...
-
Lavvas, P.
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Sagnieres, L.
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Snowden, D.
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Vuitton, V.
-
Wahlund, Jan-Eri ...
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show less...
- By the university
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