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EUV-dependence of Venusian dayside ionopause altitude:VEX and PVO observations

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Earth and Planetary Physics 2020年第1期4卷 73-81页

作者： QianQian Han markus fraenz Yong Wei Eduard Dubinin Jun Cui LiHui Chai ZhaoJin Rong WeiXing Wan Yoshifumi Futaana Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Beijing National Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100049China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Max-Planck-Institute for Solar System Research GoettingenDE 37077Germany Institutions of Earth Science Chinese Academy of SciencesBeijing 100029China School of Atmospheric Sciences Sun Yat-Sen UniversityZhuhai Guangdong 519082China Key Laboratory of Lunar and Deep Space Exploration National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China Swedish Institute of Space Physics KirunaSE 98128Sweden

The Venusian dayside ionosphere, similar to other planetary ionospheres, is produced primarily by ionization of its neutral upper atmosphere due to solar extreme ultraviolet (EUV) radiation. It has become clear that the expansion of the ionosphere may be strongly controlled by the EUV level, as exhibited in data collected by the Pioneer Venus Orbiter (PVO) during one solar cycle (1978 1992). However, the EUV-dependence of the Venusian dayside ionopause altitude, which defines the outer boundary of the ionosphere, remains obscure because the PVO crossed the dayside ionopause only during the solar maximum;its periapsis lifted too high during the solar minimum. Recently, during the period 2006 2014, which included the longest and quietest solar minimum of the past several decades, Venus Express (VEX) provided measurements of the photoelectron boundary (PEB) over the northern high-latitude region. Since the photoelectron boundary is closely related to the ionopause, we have an opportunity to analyze the EUV effect on the dayside ionopause by combining PVO and VEX observations. We have evaluated and then reduced the orbit bias effect in data from both PVO and VEX, and then used the results to derive a relationship between solar EUV level and the dayside ionopause altitude. We find that the dayside ionopause altitude increases as the solar EUV level increases, which is consistent with theoretical expectations.

关键词： Venus ionopause ionosphere solar activity

Ablation of Venusian oxygen ions by unshocked solar wind

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Science Bulletin 2017年第24期62卷 1669-1672页

作者： Yong Wei markus fraenz Edward Dubinin Weixing Wan Tielong Zhang Zhaojin Rong Lihui Chai Jun Zhong Rixiang Zhu Yoshifumi Futaana Stas Barabash Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Max-Planck-lnstitute for Solar System Research Goettingen 37077 Germany Space Research Institute Austrian Academy of Sdences Graz 8042 Austria Swedish Institute of Space Physics Kiruna SE-981 28 Sweden College of Earth Sciences University of Chinese Academy of Sciences Beijing 100049 China Institutions of Earth Science Chinese Academy of Sciences BeUing 100029 China

As an Earth-like planet Venus probably had a primordial dipole field for several million years after formation of the *** this dipole field eventually vanished the ionosphere of Venus has been exposed to the solar *** solar wind is shocked near Venus,and then scavenges the ionospheric particles through the magnetosheath and the *** escape rate of oxygen ions(O^+)estimated from spacecraft observations over the past several decades has manifested its importance for the evolution of planetary habitability,considering the accumulated effect over the history of ***,all the previous observations were made in the shocked solar wind and/or inside the wake,though some simulations showed that unshocked solar wind can also ablate O^+*** we report Venus Express observations of O^+ions in the unshocked solar wind during the solar *** observations suggest that these O^+ions are accelerated by the unshocked solar wind through pickup *** estimated O^+escape rate,2.1×10^(24) ions/s,is comparable to those measured in the shocked solar wind and the *** escape rate could result in about 2 cm global water loss over 4.5 billion *** results suggest that the atmospheric loss at unmagnetized planets is significantly underestimated by previous observations,and thus we can emphasize the importance of an Earth-like dipole for planetary habitability.

关键词： Venus Ion escape Planetary habitability

Oxygen escape from the Earth during geomagnetic reversals:Implications to mass extinction

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Oxygen escape from the Earth during geomagnetic reversals:Im...

Solar zenith angle-dependent asymmetries in Venusian bow shock location revealed by Venus Express

中国科学院地质与地球物理研究所2014年度（第14届）学术年会

作者： Yong Wei Zuyin Pu Qiugang Zong Weixing Wan Zhipeng Ren markus fraenz Eduard Dubinin Feng Tian Quanqi Shi Suiyan Fu Minghua Hong Key Laboratory of Ionospheric Environment Institute of Geology and GeophysicsChinese Academy of Sciences School of Earth and Space Sciences Peking University Max-Planck Institute for Solar System Research National Astronomical Observatories CAS Center for Earth System Sciences Tsinghua University Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and PhysicsShandong University at Weihai

The evolution of life is affected by variations of atmospheric oxygen level and geomagnetic field *** can escape into interplanetary space as ions after gaining momentum from solar wind,but Earth’s strong dipole field reduces the momentum transfer efficiency and the ion outflow rate,except for the time of geomagnetic polarity reversals when the field is significantly weakened in strength and becomes Mars-like in *** newest databases available for the Phanerozoic era illustrate that the reversal rate increased and the atmospheric oxygen level decreased when the marine diversity showed a gradual pattern of mass extinctions lasting millions of *** propose that accumulated oxygen escape during an interval of increased reversal rate could have led to the catastrophic drop of oxygen level,which is known to be a cause of mass *** simulated the oxygen ion escape rate for the Triassic-Jurassic event,using a modified Martian ion escape model with an input of quiet solar wind inferred from Sun-like *** results show that geomagnetic reversal could enhance the oxygen escape rate by 3-4 orders only if the magnetic field was extremely weak,even without consideration of space weather *** suggests that our hypothesis could be a possible explanation of a correlation between geomagnetic reversals and mass ***,if this causal relation indeed exists,it should be a "many-to-one" scenario rather the previously considered "one-to-one",and planetary magnetic field should be much more important than previously thought for planetary habitability.

关键词： atmospheric ion escape geomagnetic reversal mass extinction

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Solar zenith angle-dependent asymmetries in Venusian bow sho...

Study of fluctuations in the Martian magnetosheath using a kurtosis technique:Mars Express observations

中国科学院地质与地球物理研究所2015年度（第15届）学术年会

作者： Lihui Chai Weixing Wan markus fraenz Tielong Zhang Eduard Dubinin Yong Wei Yi Li Zhaojin Rong Jun Zhong Xiuhong Han Yoshifumi Futaana Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of Sciences CAS Key Laboratory of Geospace Environment University of Science and Technology of ChinaChinese Academy of Sciences Max-Planck-Institute for Solar System Research Space Research Institute Austrian Academy of Sciences Swedish Institute of Space Physics

It has been long known that the Venusian bow shock(BS) location is asymmetric from the observations of the long-lived Pioneer Venus Orbiter *** Venus Express(VEX) mission crossed BS near perpendicularly not only in the terminator region but also in the near-subsolar and tail *** the advantage of VEX orbit geometry,we examined a large data set of BS crossings observed during the long-lasting solar minimum between solar cycles 23 and 24 and found that the Venusian BS asymmetries exhibit dependence of solar zenith *** the terminator and tail regions,both the magnetic pole-equator and north-south asymmetries are observed in Venusian BS location,which is similar to the Pioneer Venus Orbiter(PVO) observation near ***,in the near-subsolar region,only the magnetic north-south is observed;i.e.,the BS shape is indented inward over magnetic south pole and bulged outward over magnetic north *** absence of the magnetic pole-equator asymmetry in the near-subsolar region suggests that the magnetic pole-equator asymmetry is mainly caused by the asymmetric wave propagation rather than the ion pickup *** evident magnetic north-south asymmetry in solar minimum,which is not observed by PVO,suggests that even during the low long-lasting solar minimum,the ion pickup process is very important in Venusian space environment.

关键词： The north-south asymmetry in Venusian BS location is observed in solar minimum The pole-equator asymmetry is absent in subsolar BS location The pole-equator asymmetry is caused by the asymmetric wave propagation

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Earth and Planetary Physics 2022年第1期6卷 28-41页

作者： A.M.S.Franco E.Echer M.J.A.Bolzan M.fraenz National Institute for Space Research(INPE) Sao Jose dos CamposBrazil Federal University of Jatai JataiBrazil Max Planck Institute for Solar System Research GöttingenGermany

Planetary magnetosheaths are characterized by high plasma wave and turbulence *** Martian magnetosheath is no exception;both upstream and locally generated plasma waves have been observed in the region between its bow shock and magnetic boundary layer,its induced *** statistical study of wave activity in the Martian magnetosheath is based on 12 years(2005-2016)of observations made during Mars Express(MEX)crossings of the planet’s magnetosheath-in particular,data on electron density and temperature data collected by the electron spectrometer(ELS)of the plasma analyzer(ASPERA-3)experiment on board the MEX spacecraft.A kurtosis parameter has been calculated for these plasma *** value indicates intermittent behavior in the data when it is higher than 3(the value for a normal or Gaussian distribution).The variation of wave activity occurrence has been analyzed in relation to solar cycle,Martian orbit,and distance to the bow ***-Gaussian properties are observed in the magnetosheath of Mars on all analyzed scales,especially in those near the proton gyrofrequency in the upstream region of the Martian *** also report that non-Gaussian behavior is most prominent at the smaller scales(higher frequencies).A significant influence of the solar cycle was also observed;the kurtosis parameter is higher during declining and solar maximum phases,when the presence of disturbed solar wind conditions,caused by large scale solar wind structures,*** kurtosis decreases with increasing distance from the bow shock,which indicates that the intermittence level is higher near the bow *** the electron temperature data the kurtosis is higher near the perihelion due to the higher incidence of EUV when the planet is closer to the Sun,which causes a more extended exosphere,and consequently increases the wave activity in the magnetosheath and its upstream *** extended exosphere seems to play a lower effect in the electron den

关键词： Mars magnetosheath kurtosis ULF waves