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Bidirectional electron conic observations for photoelectrons in the martian ionosphere

Earth and Planetary Physics 2020年第4期4卷 403-407页

作者： YuTian Cao Jun Cui BinBin Ni XiaoShu Wu Qiong Luo ZhaoGuo He Key Laboratory of Lunar and Deep Space Exploration National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China School of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China School of Atmospheric Sciences Sun Yat-sen UniversityZhuhaiGuangdong 519082China Center for Excellence in Comparative Planetology Chinese Academy of SciencesHefei 230026China Department of Space Physics School of Electronic InformationWuhan UniversityWuhan 430072China

Electron pitch angle distributions similar to bidirectional electron conics(BECs)have been reported at Mars in previous studies based on analyses of Mars Global Surveyor measurements.BEC distribution,also termed“butterfly”distribution,presents a local minimum flux at 90°and a maximum flux before reaching the local loss cone.Previous studies have focused on 115 eV electrons that were produced mainly via solar wind electron impact ionization.Here using Solar Wind Electron Analyzer measurements made onboard the Mars Atmosphere and Volatile Evolution spacecraft,we identify 513 BEC events for 19-55 eV photoelectrons that were generated via photoionization only.Therefore,we are investigating electrons observed in regions well away from their source regions,to be distinguished from 115 eV electrons observed and produced in the same regions.We investigate the spatial distribution of the 19-55 eV BECs,revealing that they are more likely observed on the nightside as well as near strong crustal magnetic anomalies.We propose that the 19-55 eV photoelectron BECs are formed due to day-to-night transport and the magnetic mirror effect of photoelectrons moving along cross-terminator closed magnetic field lines.

关键词： martian ionosphere photoelectron pitch angle distribution

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Modeling of kilometer-scale ionospheric irregularities at Mars

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Earth and Planetary Physics 2022年第2期6卷 213-217页

作者： ChunHua Jiang Rong Tian LeHui Wei GuoBin Yang ZhengYu Zhao School of Electronic Information Wuhan UniversityWuhan 430072China

Recently, kilometer-scale martian ionospheric irregularities have been measured by the Mars Atmosphere and Volatile EvolutioN(MAVEN) mission(Fowler et al., 2020). In this study, we carried out a simulation of these irregularities, assuming a uniform martian zonal neutral wind and a cosinusoidal perturbation of the plasma density as the seeding source. Results show that a vertical electric field shear could be induced by such a plasma density perturbation. We find that the vertical electric field shear causes a velocity shear of the plasma between the topside and bottomside ionosphere, which in turn is able to produce kilometer-scale ionospheric irregularities — irregularities of a smaller scale than were seen in previous simulations(Jiang CH et al., 2021). These kilometer-scale variations with altitude, in plasma density and magnetic field profiles, are comparable to the MAVEN observations.

关键词： martian ionosphere ionospheric irregularities numerical simulation

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

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Earth and Planetary Physics 2020年第4期4卷 396-402页

作者： Hao Gu Jun Cui DanDan Niu LongKang Dai JianPing Huang XiaoShu Wu YongQiang Hao Yong Wei State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyMacao 999078China School of Atmospheric Sciences Sun Yat-Sen UniversityZhuhai Guangdong 519082China Key Laboratory of Lunar and Deep Space Exploration Chinese Academy of SciencesBeijing 100101China Chinese Academy of Sciences Center for Excellence in Comparative Planetology Hefei 230026China School of Earth and Space Sciences Beijing UniversityBeijing 100871China Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China School of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

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.

关键词： MAVEN martian ionosphere dication

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Ionogram inversion for MARSIS topside sounding

Ionogram inversion for MARSIS topside sounding

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中国科学院地质与地球物理研究所2012年度（第12届）...

作者： Xiuhong Han Weixing Wan Beijing National Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of Sciences Graduate University of Chinese Academy of Sciences

In the present paper,we propose a method of ionogram inversion to retrieve the electron density profile,N(h), of the martian ionosphere from the topside ionogram,which is measured by the Mars Advanced Radar for Subsurface and ionosphere Sounding(MARSIS) instrument on board the Mars Express spacecraft.The new inversion technique is developed from Titheridge’s method by replacing the prior polynomials with empirical orthogonal functions(EOFs),which are estimated from the archived N(h) observation by the radio occultation of Mars Global Surveyor(MGS).The EOF-based technique has achieved quick convergence and good stability. It is concluded that the newly developed method is an alternative tool for the analysis of MARSIS ionograms.

关键词： martian ionosphere MARSIS ionogram ionogram inversion

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