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| 1 | The solar wind plasma upstream of Mars observed by Tianwen-1:Comparison with Mars Express and MAVEN显示文摘On the great journey to Mars,China’s first planetary exploration mission,the Tianwen-1 came within 26 million kilometers of Mars from 31 October 2020 to 25 January 2021 and was getting closer to its destination,the red planet,in search of answers to the cataclysmic climate change that occurred in Martian history.Both the escape of the Martian atmosphere and the loss of surface water were firmly influenced by solar activities.Tianwen-1 provided a unique chance to depict the solar wind streams between Earth and Mars during the minimum of Solar Cycle 25.During the three-month cruise phase of Tianwen-1,the solar wind flows were successively observed at Earth,Tianwen-1,and Mars.After the field of view correction and noise reduction,the solar wind velocity and density measured by Tianwen-1 show good agreement with those at Earth and Mars.The results indicate that the performance of the ion analyzer onboard the Tianwen-1 orbiter is reliable and stable.It is worth looking forward to the joint observations of ion escape with other Mars probes in the following Martian years. | Kai FAN Limei YAN Yong WEI Aibing ZHANG Linggao KONG Markus FRÄNZ Fei HE Lihui CHAI Chongjing YUAN Yuqi WANG Jun ZHONG Zhaojin RONG Zhonghua YAO Yongxin PAN Jun CUI Jiansen HE Wenya LI Binbin TANG Chi WANG | 2022 | Science China Earth Sciences2022，65，4： | 2 |
| 2 | Distribution and transport characteristics of fine particulate matter in beijing with mobile lidar measurements from 2015 to 2018显示文摘Accurately quantifying the concentration and transport flux of atmospheric fine particu-late matter(PM_(2.5))is vital when attempting to thoroughly identify the pollution formation mechanism.In this study,the mobile lidar measurements in Beijing on heavily polluted days in December from 2015 to 2018 are presented.The lidar was mounted on a vehicle,which could perform measurements along designated routes.On the basis of mobile lidar mea-surements along closed circuits of the 6th Ring Road around Beijing,the spatial distribution and transport flux of PM_(2.5) in Beijing were determined with information of wind field.In the spatial distribution,both the concentration and transport of PM_(2.5) were revealed to be more significant in the southern section of Beijing.The regional transport layer at heights<1.3 km plays an important role in pollution formation.The maximum transport flux reached 1600μg/(m^(2)*sec)on 11 December 2016.With the aerosol boundary layer height determined from the image edge detection(IED)method,the inter-annual variations of the aerosol boundary layer height(ABLH)were also analysed.The ABLH decreased from 0.73 to 0.46 km during the same heavy pollution period from 2015 to 2018.Increasingly adverse aerosol boundary layer(ABL)meteorological factors,including lower ABLH,light winds,temperature inversions,and accumulated moisture,have become necessary for pollution formation in Beijing. | Lihui Lv Tianshu Zhang Yan Xiang Wenxuan Chai Wenqing Liu | 2022 | Journal of Environmental Sciences2022，34，5： | 1 |
| 3 | EUV-dependence of Venusian dayside ionopause altitude:VEX and PVO observations显示文摘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. | QianQian Han Markus Fraenz Yong Wei Eduard Dubinin Jun Cui LiHui Chai ZhaoJin Rong WeiXing Wan Yoshifumi Futaana | 2020 | Earth and Planetary Physics2020，4，1： | 1 |
| 4 | Low-frequency waves in magnetic reconnection显示文摘The characteristics of low-frequency waves in magnetic reconnection are studied using two-dimensional hybrid simulation code. In a coordinate system moving with fluid,the time series of a magnetic field perpendicular to the magnetic reconnection plane,By, is transformed into the power spectrum via fast Fourier transformation,while the wave propagation direction and polarization are determined by minimum variance analysis of the electric field.The results show that low-frequency Alfvén ion-cyclotron waves dominate the reconnection area.These waves have frequencies 0-1Ωp(where Ωp is the local proton gyro frequency)and all are left-handed circularly polarized.Among these waves,large-amplitude turbulence,with frequencies of 0-0.6Ωp and isotropic propagation,dominates the outflow regions.This can cause the reversal of By in the quadrupole structure.In the inflow regions, dominant waves,propagating mainly parallel to the ambient magnetic field,have higher frequencies and smaller amplitudes.The frequency of the main peak of wave energy is usually higher than 0.5Ωp. | CHAI LiHui LI Yi WANG Shui SHEN Chao | 2012 | Chinese Science Bulletin2012，57，12： | 0 |
| 5 | Frozen Gaussian Approximation for the Dirac Equation in Curved Space with Application to Strained Graphene显示文摘In this paper,we derive the frozen Gaussian approximation(FGA)for computing the solution to the Dirac equation in curved space in the semi-classical regime.The latter equation is used in particular for modeling electronic scattering on strained graphene surfaces.We present numerical comparisons of the Dirac solutions on curved and flat spaces,illustrating the focusing effect of graphene surfaces,as well as qualitative comparisons with a tight-binding model.A CPU-time comparison shows that FGA becomes more efficient than an IMEX pseudospectral method when the semiclassical parameter is small. | Lihui Chai Lorin Emmanuel Xu Yang | 2023 | Communications in Computational Physics2023，33，6： | 0 |
| 6 | Ablation of Venusian oxygen ions by unshocked solar wind显示文摘As an Earth-like planet Venus probably had a primordial dipole field for several million years after formation of the planet.Since this dipole field eventually vanished the ionosphere of Venus has been exposed to the solar wind.The solar wind is shocked near Venus,and then scavenges the ionospheric particles through the magnetosheath and the magnetotail.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 Venus.However,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^+ions.Here we report Venus Express observations of O^+ions in the unshocked solar wind during the solar minimum.The observations suggest that these O^+ions are accelerated by the unshocked solar wind through pickup processes.The estimated O^+escape rate,2.1×10^(24) ions/s,is comparable to those measured in the shocked solar wind and the wake.This escape rate could result in about 2 cm global water loss over 4.5 billion years.Our 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. | Yong Wei Markus Fraenz Edward Dubinin Weixing Wan Tielong Zhang Zhaojin Rong Lihui Chai Jun Zhong Rixiang Zhu Yoshifumi Futaana Stas Barabash | 2017 | Science Bulletin2017，62，24： | 0 |
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