Observation of CO2^++ dication in the dayside Martian upper atmosphere

作     者：Hao Gu Jun Cui DanDan Niu LongKang Dai JianPing Huang XiaoShu Wu YongQiang Hao Yong Wei Hao Gu;Jun Cui;DanDan Niu;LongKang Dai;JianPing Huang;XiaoShu Wu;YongQiang Hao;Yong Wei

作者机构：State Key Laboratory of Lunar and Planetary SciencesMacao University of Science and TechnologyMacao 999078China School of Atmospheric SciencesSun Yat-Sen UniversityZhuhai Guangdong 519082China Key Laboratory of Lunar and Deep Space ExplorationChinese Academy of SciencesBeijing 100101China Chinese Academy of Sciences Center for Excellence in Comparative PlanetologyHefei 230026China School of Earth and Space SciencesBeijing UniversityBeijing 100871China Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China School of Earth and Planetary SciencesUniversity of Chinese Academy of SciencesBeijing 100049China 

出 版 物：《Earth and Planetary Physics》 (地球与行星物理（英文版）)

年 卷 期：2020年第4卷第4期

页      面：396-402页

核心收录：

学科分类：07[理学] 0708[理学-地球物理学] 070401[理学-天体物理] 0704[理学-天文学] 

基　　金：supported by the B-type Strategic Priority Program No.XDB41000000 funded by the Chinese Academy of Sciences,and the pre-research projects on Civil Aerospace Technologies No.D020105 and D020103 funded by China's National Space Administration the National Science Foundation of China through grants 41525015 and 41774186 to JC,41904154 to WXS,and 41525016 to YW. 

主　　题：MAVEN Martian ionosphere dication 

摘      要：Doubly charged positive ions(dications)are an important component of planetary ionospheres because of the large energy required for their formation.Observations of these ions are exceptionally difficult due to their low abundances;until now,only atomic dications have been detected.The Neutral Gas and Ion Mass Spectrometer(NGIMS)measurements made on board the recent Mars Atmosphere and Volatile Evolution mission provide the first opportunity for decisive detection of molecular dications,CO2^++in this case,in a planetary upper atmosphere.The NGIMS data reveal a dayside averaged CO2^++distribution declining steadily from 5.6 cm^−3 at 160 km to below 1 cm^−3 above 200 km.The dominant CO2^++production mechanisms are double photoionization of CO2 below 190 km and single photoionization of CO2^+at higher altitudes;CO2++destruction is dominated by natural dissociation,but reactions with atmospheric CO2 and O become important below 160 km.Simplified photochemical model calculations are carried out and reasonably reproduce the data at low altitudes within a factor of 2 but underestimate the data at high altitudes by a factor of 4.Finally,we report a much stronger solar control of the CO2^++density than of the CO2+density.