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SUPRATHERMAL ELECTRONS IN TITAN’S SUNLIT IONOSPHERE: MODEL–OBSERVATION COMPARISONS
Vigren,E.1; Galand,M.2; Wellbrock,A.3; Coates,A. J.3; Cui,J.4,5; Edberg,N. J. T.1; Lavvas,P.6; Sagnières,L.2; Snowden,D.7; Vuitton,V.8; Wahlund,J.-E.1
2016-07-27
Source PublicationThe Astrophysical Journal
ISSN0004-637X
Volume826Issue:2
AbstractABSTRACT The dayside ionosphere of the Saturnian satellite Titan is generated mainly from photoionization of N2 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 N2 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 ~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.
Keywordmolecular processes planets and satellites: individual (Titan)
DOI10.3847/0004-637X/826/2/131
Language英语
WOS IDIOP:0004-637X-826-2-131
PublisherThe American Astronomical Society
Citation statistics
Document Type期刊论文
Identifierhttp://ir.bao.ac.cn/handle/114a11/36312
Collection中国科学院国家天文台
Affiliation1.Swedish Institute of Space Physics, Uppsala, Sweden; erik.vigren@irfu.se
2.Department of Physics, Imperial College London, London SW7 2AZ, UK
3.Mullard Space Science Laboratory, University College London, Dorking, Surrey RH5 6NT, UK
4.National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
5.Lunar and Planetary Science Laboratory, Macau University of Science and Technology, Macau, China
6.Université Reims Champagne-Ardenne, Reims, France
7.Department of Physics, Central Washington University, Ellensburg, WA 98926, USA
8.Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France
Recommended Citation
GB/T 7714
Vigren,E.,Galand,M.,Wellbrock,A.,等. SUPRATHERMAL ELECTRONS IN TITAN’S SUNLIT IONOSPHERE: MODEL–OBSERVATION COMPARISONS[J]. The Astrophysical Journal,2016,826(2).
APA Vigren,E..,Galand,M..,Wellbrock,A..,Coates,A. J..,Cui,J..,...&Wahlund,J.-E..(2016).SUPRATHERMAL ELECTRONS IN TITAN’S SUNLIT IONOSPHERE: MODEL–OBSERVATION COMPARISONS.The Astrophysical Journal,826(2).
MLA Vigren,E.,et al."SUPRATHERMAL ELECTRONS IN TITAN’S SUNLIT IONOSPHERE: MODEL–OBSERVATION COMPARISONS".The Astrophysical Journal 826.2(2016).
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