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The anisotropy of suprathermal electrons in the Martian ionosphere

Earth and Planetary Physics 2024年第3期8卷 459-471页

作者： yutian cao Jun Cui XiaoShu Wu WenJun Liang RuiQi Fu HaoYu Lu Planetary Environmental and Astrobiological Research Laboratory(PEARL) School of Atmospheric SciencesSun Yat-sen UniversityZhuhai 519082China Key Laboratory of Geospace Environment University of Science&Technology of ChinaChinese Academy of SciencesHefei 230026China Center for Excellence in Comparative Planetology Chinese Academy of SciencesHefei 230026China School of Space and Environment Beihang UniversityBeijing 102206China

Suprathermal electrons are an important population of the Martian ionosphere, either produced by photoionization of atmospheric neutrals or supplied from the Solar Wind (SW). This study is dedicated to an in-depth investigation of the pitch angle distribution of suprathermal electrons at two representative energies, 19−55 eV and 124−356 eV, using the extensive measurements made by the Solar Wind Electron Analyzer on board the Mars Atmosphere and Volatile Evolution. Throughout the study, we focus on the overall degree of anisotropy, defined as the standard deviation of suprathermal electron intensity among different directions which is normalized by the mean omni-directional intensity. The available data reveal the following characteristics: (1) In general, low energy electrons are more isotropic than high energy electrons, and dayside electrons are more isotropic than nightside electrons;(2) On the dayside, the anisotropy increases with increasing altitude at low energies but remains roughly constant at high energies, whereas on the nightside, the anisotropy decreases with increasing altitude at all energies;(3) Electrons tend to be more isotropic in strongly magnetized regions than in weakly magnetized regions, especially on the nightside. These observations indicate that the anisotropy is a useful diagnostic of suprathermal electron transport, for which the conversion between the parallel and perpendicular momenta as required by the conservation of the first adiabatic invariant, along with the atmospheric absorption at low altitudes, are two crucial factors modulating the observed variation of the anisotropy. Our analysis also highlights the different roles on the observed anisotropy exerted by suprathermal electrons of different origins.

关键词： Mars ionosphere suprathermal electron pitch angle distribution

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The response of Martian photoelectron boundary to the 2018 global dust storm

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Science China Earth Sciences 2024年第9期67卷 2772-2782页

作者： Yuqi WANG Jun CUI Yong WEI Zhaopeng WU Kai FAN Zhaojin RONG Fei HE yutian cao Jiawei GAO Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of Sciences College of Earth and Planetary Sciences University of Chinese Academy of Sciences Planetary Environmental and Astrobiological Research Laboratory (PEARL) School of Atmospheric SciencesSun Yat-sen University Center for Excellence in Comparative Planetology Chinese Academy of Sciences

Extensive research efforts have revealed that the Martian dust storms can perturb the upper atmospheric condition and as a consequence, enhance plasma density and photoelectron flux in the ionosphere. However, previous observational studies of the Martian dust storm impacts have been restricted to regions below 400 km, which limits our understanding of the Martian dust storm effects in the upper ionosphere and magnetosphere. Here, based on the suprathermal electron measurements made by the Solar Wind Electron Analyzer onboard the Mars Atmosphere and Volatile Evolution, we identify with an automatic procedure the occurrences of all photoelectron boundary(PEB) crossings at solar zenith angle below 120°(with a dust-free median altitude of about 600 km). Using the dayside PEB as a proxy of the upper ionospheric and magnetospheric condition, we analyze the variations of the PEB altitude during the 2018 global dust storm(GDS) of Mars Year 34(MY34) and compare them with the period in MY33 when there was no global dust storm. We conclude that the column dust optical depth(CDOD) emerges as one of the main driving factors for PEB altitude variations during the GDS. Our analysis implies that the GDS can affect the Martian upper atmosphere and ionosphere over considerable distances and extended time scales.

关键词： Martian global dust storm Martian photoelectron boundary Upper ionosphere

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A general climatology of categorized Martian ionospheric irregularities

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Science China Earth Sciences 2024年

作者： Xin WAN Jiahao ZHONG Yongqiang HAO Chao XIONG Hui WANG yutian cao Jun CUI Yiwen LIU Qiaoling LI Jiawei KUAI Planetary Environmental and Astrobiological Research Laboratory (PEARL) School of Atmospheric Sciences Sun Yat-sen University Key Laboratory of Tropical Atmosphere-Ocean System Ministry of Education Department of Space Physics College of Electronic Information Luojia Laboratory Wuhan University School of Physics and Electronic Information Shangrao Normal University School of Petroleum China University of Petroleum-Beijing at Karamay College of Astronautics Nanjing University of Aeronautics and Astronautics

A climatological survey of Martian ionospheric plasma density irregularities was conducted by exploring the in-situ measurements of the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. The irregularities were first classified as enhancement, depletion, and oscillation. By checking the simultaneous magnetic field fluctuation, the irregularities have been classified into two types:with or without magnetic signatures. The classified irregularities exhibit diverse global occurrence patterns, as those with magnetic signatures tend to appear near the periphery of the crustal magnetic anomaly (MA), and those without magnetic signatures prefer to appear either inside of the MA or outside of the MA, depending on the type and solar zenith angle. Under most circumstances, the irregularities have a considerable occurrence rate at altitudes above the ionospheric dynamo height (above 200 km), and the magnetization state of the ions seems irrelevant to their occurrence. In addition, the irregularities do not show dependence on magnetic field geometry, except that the enhancement without magnetic signatures favors the vertical field line, implying its equivalence to the localized bulge. Other similarities and discrepancies exist in reference to previous studies. We believe this global survey complements previous research and provides crucial research clues for future efforts to clarify the nature of the Martian ionospheric irregularities.

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Photoelectron pitch angle distribution near Mars and implications on cross terminator magnetic field connectivity

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Earth and Planetary Physics 2020年第1期4卷 17-22页

作者： yutian cao Jun Cui XiaoShu Wu JiaHao Zhong 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 UniversityZhuhai Guangdong 519082China Center for Excellence in Comparative Planetology Chinese Academy of SciencesHefei 230026China

The photoelectron peak at 22 27 eV, a distinctive feature of the energetic electron distribution in the dayside Martian ionosphere, is a useful diagnostic of solar extreme ultraviolet (EUV) and X-ray ionization as well as of large-scale transport along magnetic field lines. In this work, we analyze the pitch angle distribution (PAD) of energetic electrons at 22 27 eV measured during several representative Mars Atmosphere and Volatile Evolution (MAVEN) orbits, based on the electron spectra gathered by MAVEN’s Solar Wind Electron Analyzer (SWEA) instrument. On the dayside, most photoelectron spectra show an isotropic PAD as is expected from production via solar EUV/X-ray ionization. The photoelectron spectra occasionally observed on the nightside show instead a strongly anisotropic PAD, indicative of cross-terminator transport along ambient magnetic field lines. This would in turn predict the presence of dayside photoelectrons, also with a strongly anisotropic PAD, which was indeed revealed in SWEA data. Comparison with magnetic field measurements made by the MAVEN Magnetometer suggests that on average the photoelectrons with anisotropic PAD stream away from Mars on the dayside and towards Mars on the nightside, further supporting the scenario of day-to-night transport. On both sides, anisotropic photoelectrons tend to be observed above the photoelectron exobase at ~160 km where photoelectron transport dominates over local production and energy degradation.

关键词： Mars MAVEN photoelectron Day-to-night transport

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Response of photoelectron peaks in the Martian ionosphere to solar EUV/X-ray irradiance

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Earth and Planetary Physics 2020年第4期4卷 390-395页

作者： XiaoShu Wu Jun Cui yutian cao WeiQin Sun Qiong Luo BinBin Ni National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China Planetary Environmental and Astrobiological Research Laboratory(PEARL) School of Atmospheric SciencesSun Yat-sen UniversityZhuhai Guangdong 519082China Chinese Academy of Sciences Center for Excellence in Comparative Planetology Hefei 230026China Department of Space Physics School of Electronic InformationWuhan UniversityWuhan 430074China

An important population of the dayside Martian ionosphere are photoelectrons that are produced by solar Extreme Ultraviolet and X-ray ionization of atmospheric neutrals.A typical photoelectron energy spectrum is characterized by a distinctive peak near 27 eV related to the strong solar HeⅡ emission line at 30.4 nm,and an additional peak near 500 eV related to O Auger *** this study,the extensive measurements made by the Solar Wind Electron Analyzer on board the recent Mars Atmosphere and Volatile Evolution spacecraft are analyzed and found to verify the scenario that Martian ionosphere photoelectrons are driven by solar *** report that the photoelectron intensities at the centers of both peaks increase steadily with increasing solar ionizing flux below 90 nm and that the observed solar cycle variation is substantially more prominent near the O Auger peak than near the HeⅡ *** latter observation is clearly driven by a larger variability in solar irradiance at shorter *** the solar ionizing flux increases from 1 mW·m^-2 to 2.5 mW·m^-2,the photoelectron intensity increases by a factor of 3.2 at the HeⅡ peak and by a much larger factor of 10.5 at the O Auger peak,both within the optically thin regions of the Martian atmosphere.

关键词： Mars ionosphere photoelectron solar irradiance MAVEN

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Bidirectional electron conic observations for photoelectrons in the Martian ionosphere

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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 *** distribution,also termed“butterfly”distribution,presents a local minimum flux at 90°and a maximum flux before reaching the local loss *** studies have focused on 115 eV electrons that were produced mainly via solar wind electron impact *** 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 ***,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 *** 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 *** 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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Is Solar Wind electron precipitation a source of neutral heating in the nightside Martian upper atmosphere?

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Earth and Planetary Physics 2021年第1期5卷 1-10页

作者： LongKang Dai Jun Cui DanDan Niu Hao Gu yutian cao XiaoShu Wu HaiRong Lai Planetary Environmental and Astrobiological Research Laboratory(PEARL) School of Atmospheric SciencesSun Yat-sen UniversityZhuhai Guangdong 519082China Key Laboratory of Lunar and Deep Space Exploration National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Center for Excellence in Comparative Planetology Chinese Academy of SciencesHefei 230031China Institute of Space Science and Applied Technology Harbin Institute of TechnologyShenzhen Guangdong 518055China

Solar Wind(SW)electron precipitation is able to deposit a substantial amount of energy in the nightside Martian upper atmosphere,potentially exerting an influence on its thermal *** study serves as the first investigation of such an issue,with the aid of the simultaneous measurements of both neutral density and energetic electron intensity made on board the recent Mars Atmosphere and Volatile Evolution(MAVEN)*** report that,from a statistical point of view,the existing measurements do not support a scenario of noticeable neutral heating via SW electron ***,during 3%−4%of the MAVEN orbits for which data are available,strong correlation between nightside temperature and electron intensity is observed,manifested as collocated enhancements in both parameters,as compared to the surrounding *** addition,our analysis also indicates that neutral heating via SW electron precipitation tends to be more effective at altitudes below 160 km for integrated electron intensities above 0.01 ergs·cm^−2·s^−1 over the energy range of 3−450 *** results reported here highlight the necessity of incorporating SW electron precipitation as a heat source in the nightside Martian upper atmosphere under extreme circumstances such as during interplanetary coronal mass ejections.

关键词： Mars Solar Wind upper atmosphere MAVEN

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A survey of total electron content depression in the nightside Martian ionosphere

A survey of total electron content depression in the nightsi...

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作者： cao yutian Cui Jun Wu Xiaoshu Sun Yat-sen University

Thermal electron depression and energetic electron depletion are two well-known features of the nightside Martian *** the latter has been extensively studied in the past,there is no report of systematic and firm ident... 详细信息

关键词： A survey of total electron content depression in the nightside Martian ionosphere

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The anisotropy of suprathermal electrons in the Martian ionosphere

The anisotropy of suprathermal electrons in the Martian iono...

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2020年中国地球科学联合学术年会

作者： yutian cao Jun Cui Hairong Lai Binbin Ni Dandan Niu Xiaoshu Wu School of Atmospheric Sciences Sun Yat-sen University Department of Space Physics School of Electronic Information Wuhan University Space Science Institute Macau University of Science and Technology Key Laboratory of Lunar and Deep Space Exploration National Astronomical Observatories Chinese Academy of Sciences

关键词： The anisotropy of suprathermal electrons in the Martian ionosphere

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水泥乳化沥青混合料路面压实工艺参数研究

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重庆交通大学学报（自然科学版） 2024年第4期43卷 14-19,29页

作者：张翠红窦益华曹学鹏贺雨田西安石油大学机械工程学院陕西西安710065 西安石油大学西安市高难度复杂油气井完整性评价重点实验室陕西西安710065 长安大学道路施工技术与装备教育部重点实验室陕西西安710064

为了精准预测水泥乳化沥青混合料路面达到目标密实度所需的压路机压实工艺参数组合,基于该混合料压实流变时变特性及压实Bodner-Partom(B-P)本构模型,采用数值仿真和路面压实试验相结合的方法开展研究。首先对ANSYS进行二次开发得到B-P... 详细信息

为了精准预测水泥乳化沥青混合料路面达到目标密实度所需的压路机压实工艺参数组合,基于该混合料压实流变时变特性及压实Bodner-Partom(B-P)本构模型,采用数值仿真和路面压实试验相结合的方法开展研究。首先对ANSYS进行二次开发得到B-P材料模型,然后将阶段性变化的B-P模型参数代入压实组合仿真分析中,最后开展路面压实试验,进一步得到压实工艺参数优化组合。数值仿真研究结果表明:由仿真结果得到3个低频高幅高速组合,3个组合作用后沿轮宽方向的混合料竖向应变值减小幅度均较大,在路面深度6 cm处的混合料竖向应变衰减幅度值均较小,其中组合六的衰减幅度值为最小,路面目标成型厚度可控制在7 cm以下。路面压实试验表明,组合六(低频高幅高速压实6遍)的有效压实能量偏大,应将组合六的压实遍数优化为:低频高幅高速压实5遍+高频低幅高速压实2遍。

关键词：道路工程水泥乳化沥青混合料压实流变时变特性 B-P本构模型参数路面压实工艺参数组合

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