Field-Aligned Photoelectron Energy Peaks at High Altitude and on the Nightside of Titan
文献类型：期刊论文
| 作者 | Cao, Y. -T.1,2,3,7; Wellbrock, A.2,7; Coates, A. J.2,7; Caro-Carretero, R.2,4,7; Jones, G. H.2,7; Cui, J.3,5; Galand, M.6; Dougherty, M. K.6 |
| 刊名 | JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
 |
| 出版日期 | 2020 |
| 卷号 | 125期号:1页码:13 |
| ISSN号 | 2169-9097 |
| DOI | 10.1029/2019JE006252 |
| 英文摘要 | The ionization of N-2 by strong solar He II 30.4-nm photons produces distinctive spectral peaks near 24.1 eV in Titan's upper atmosphere, which have been observed by the Electron Spectrometer (ELS) as part of the Cassini Plasma Spectrometer. The ELS observations reveal that, in addition to the dayside, photoelectron peaks were also detected on the deep nightside where photoionization is switched off, as well as at sufficiently high altitudes where the ambient neutral density is low. These photoelectron peaks are unlikely to be produced locally but instead must be contributed by transport along the magnetic field lines from their dayside source regions. In this study, we present a statistical survey of all photoelectron peaks identified with an automatic finite impulse response algorithm based on the available ELS data accumulated during 56 Titan flybys. The spatial distribution of photoelectron peaks indicates that most photoelectrons detected at an altitude above 4,000 km and a solar zenith angle above 100 degrees are field aligned, which is consistent with the scenario of photoelectron transport along the magnetic field lines. Our analysis also reveals the presence of a photoelectron gap in the deep nightside ionosphere where almost no photoelectrons were detected. It appears to be very difficult for photoelectrons to travel to this region, and such a feature may not be driven by the changes in the orientation between the solar and corotation wakes. Plain Language Summary The strong solar Extreme Ultraviolet radiation generates photoelectrons with spectral peaks near 24.1 eV in the Titan's dayside ionosphere, which have been observed by the Electron Spectrometer (ELS), part of the Cassini Plasma Spectrometer. In addition to the dayside, ELS also detected photoelectron peaks on the nightside where solar radiation is switched off and at large distances from Titan where the ambient neutral density is extremely low. These photoelectron peaks are, therefore, more likely contributed by transport along the magnetic field lines from the dayside. We present a statistical survey of all photoelectron peaks identified with an automatic algorithm based on the available ELS data. Our analysis confirms that most photoelectrons detected at high altitudes and in the deep nightside move along magnetic field lines. Besides, our result reveals, for the first time, the presence of a photoelectron gap on the nightside. However, no viable mechanism, such as the Saturn local time variation, could explain the gap. |
| WOS关键词 | IONOSPHERIC PHOTOELECTRONS ; CASSINI ; PLASMA ; MAGNETOSPHERE ; ATMOSPHERE ; VICINITY ; FLUXES |
| 资助项目 | UK Science and Technology Facilities Council[ST/S000240/1] ; Ministerio de Economia y Competitividad of Spain[ESP2016-79135-R] ; STFC of UK[ST/N000692/4] ; National Science Foundation of China[41525015] ; National Science Foundation of China[41774186] ; UCAS |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:000520141700007 |
| 出版者 | AMER GEOPHYSICAL UNION |
| 资助机构 | UK Science and Technology Facilities Council ; UK Science and Technology Facilities Council ; Ministerio de Economia y Competitividad of Spain ; Ministerio de Economia y Competitividad of Spain ; STFC of UK ; STFC of UK ; National Science Foundation of China ; National Science Foundation of China ; UCAS ; UCAS ; UK Science and Technology Facilities Council ; UK Science and Technology Facilities Council ; Ministerio de Economia y Competitividad of Spain ; Ministerio de Economia y Competitividad of Spain ; STFC of UK ; STFC of UK ; National Science Foundation of China ; National Science Foundation of China ; UCAS ; UCAS ; UK Science and Technology Facilities Council ; UK Science and Technology Facilities Council ; Ministerio de Economia y Competitividad of Spain ; Ministerio de Economia y Competitividad of Spain ; STFC of UK ; STFC of UK ; National Science Foundation of China ; National Science Foundation of China ; UCAS ; UCAS ; UK Science and Technology Facilities Council ; UK Science and Technology Facilities Council ; Ministerio de Economia y Competitividad of Spain ; Ministerio de Economia y Competitividad of Spain ; STFC of UK ; STFC of UK ; National Science Foundation of China ; National Science Foundation of China ; UCAS ; UCAS |
| 源URL | [http://ir.bao.ac.cn/handle/114a11/56400]  |
| 专题 | 中国科学院国家天文台 |
| 通讯作者 | Cao, Y. -T. |
| 作者单位 | 1.Chinese Acad Sci, Natl Astron Observ, Key Lab Lunar & Deep Space Explorat, Beijing, Peoples R China 2.UCL Birkbeck, Ctr Planetary Sci, London, England 3.Univ Chinese Acad Sci, Sch Astron & Space Sci, Beijing, Peoples R China 4.Univ Pontificia ICAI ICADE Comillas, Madrid, Spain 5.Sun Yat Sen Univ, Sch Atmospher Sci, Zhuhai, Peoples R China 6.Imperial Coll London, Dept Phys, London, England 7.UCL, Dept Space & Climate Phys, Mullard Space Sci Lab, London, England |
| 推荐引用方式 GB/T 7714 | Cao, Y. -T.,Wellbrock, A.,Coates, A. J.,et al. Field-Aligned Photoelectron Energy Peaks at High Altitude and on the Nightside of Titan[J]. JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS,2020,125(1):13. |
| APA | Cao, Y. -T..,Wellbrock, A..,Coates, A. J..,Caro-Carretero, R..,Jones, G. H..,...&Dougherty, M. K..(2020).Field-Aligned Photoelectron Energy Peaks at High Altitude and on the Nightside of Titan.JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS,125(1),13. |
| MLA | Cao, Y. -T.,et al."Field-Aligned Photoelectron Energy Peaks at High Altitude and on the Nightside of Titan".JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 125.1(2020):13. |
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来源：国家天文台
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