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Recent ionospheric investigations in China(2018–2019)

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Earth and Planetary Physics 2020年第3期4卷 179-205页

作者： LiBo Liu weixing wan Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China Beijing National Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100101China College of Earth and Planetary Sciences University of the Chinese Academy of SciencesBeijing 100019China

Since the release of the 2018 National Report of China on ionospheric research(Liu LB and wan WX,2018)to the Committee on Space Research(COSPAR),scientists from China's Mainland have made many new fruitful investigations of various ionospheric-related issues.In this update report,we briefly introduce more than 130 recent reports(2018–2019).The current report covers the following topics:ionospheric space weather,ionospheric structures and climatology,ionospheric dynamics and couplings,ionospheric irregularity and scintillation,modeling and data assimilation,and radio wave propagation in the ionosphere and sounding techniques.

关键词： ionosphere ionospheric storm ionospheric climatology ionospheric irregularity GNSS space weather

New understanding achieved from 2 years of Chinese ionospheric investigations

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Science Bulletin 2016年第7期61卷 524-542页

作者： Libo Liu weixing wan Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences Beijing National Observatory of Space Environment Institute of Geology and Geophysics Chinese Academy of Sciences Geoscience School University of the Chinese Academy of Sciences

In the mainland of China, the number of ionospheric research groups is more than 10. Around 110 articles related to ionospheric physics have been published during 2014–2015. In this annual national report of the Committee on Space Research(COSPAR), we will outline some recent progresses in ionospheric studies conducted by the Chinese mainland scientists in the past 2 years. These investigations cover(1) the ionosphere responses to geomagnetic activities;(2) ionospheric climatology and structures;(3) couplings between the ionosphere, plasmasphere and lower atmosphere, and possible seismic signatures in the ionosphere;(4) ionospheric irregularities and scintillation;(5) ionospheric models, data assimilation and simulations;(6) ionospheric dynamics and electrodynamics;(7) progresses in the observation methodology and technique; and(8) planetary ionospheres. Such investigations will strengthen our ability to monitor the ionosphere,provide a better understanding of the ionospheric states and the underlying fundamental processes, and improve the ionospheric modeling, forecasting, and related applications.

关键词：电离层耦合中国大陆电离层闪烁电离层模型物理相关地球磁场低层大气地震信号

Wavenumber-4 spectral component extracted from TIMED/SABER observations

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Earth and Planetary Physics 2020年第5期4卷 436-448页

作者： Xing Li weixing wan JinBin Cao ZhiPeng Ren Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China School of Space and Environment Beihang UniversityBeijing 100083China Key Laboratory of Space Environment Monitoring and Information Processing Ministry of Industry and Information TechnologyBeijing 100083China Beijing National Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China University of the Chinese Academy of Sciences Beijing 100049China

The wavenumber spectral components WN4 at the mesosphere and low thermosphere(MLT)altitudes(70–10 km)and in the latitude range between±45°are obtained from temperature data(T)observed by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instruments on board the National Aeronautics and Space Administration(NASA)’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics(TIMED)spacecraft during the 11-year solar period from 2002 to 2012.We analyze in detail these spectral components WNk and obtain the main properties of their vertical profiles and global structures.We report that all of the wavenumber spectral components WNk occur mainly around 100 km altitude,and that the most prominent component is the wavenumber spectral component WN4 structure.Comparing these long duration temperature data with results of previous investigations,we have found that the yearly variation of spectral component WN4 is similar to that of the eastward propagating non-migrating diurnal tide with zonal wavenumber 3(DE3)at the low latitudes,and to that of the semi-diurnal tide with zonal wavenumber 2(SE2)at the mid-latitudes:the amplitudes of the A4 are larger during boreal summer and autumn at the low-latitudes;at the mid-latitudes the amplitudes have a weak peak in March.In addition,the amplitudes of component WN4 undergo a remarkable short period variation:significant day-to-day variation of the spectral amplitudes A4 occurs primarily in July and September at the low-latitudes.In summary,we conclude that the non-migrating tides DE3 and SE2 are likely to be the origins,at the low-latitudes and the mid-latitudes in the MLT region,respectively,of the observed wavenumber spectral component WN4.

关键词： TIMED observations wavenumber spectral components non-migrating tides short period variation

The source of tropospheric tides

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Earth and Planetary Physics 2020年第5期4卷 449-460页

With the method of Hough mode decomposition(HMD),the tidal sources of the three main tidal components,namely,the migrating components DW1(diurnal westward propagating wavenumber 1)and SW2(semidiurnal westward propagating wavenumber 2)and the non-migrating component DE3(diurnal eastward propagating wavenumber 3),at the tropospheric altitudes(1–12 km)and in the latitude range of±60°,were obtained from National Centers for Environmental Prediction(NCEP)Climate Forecast System Reanalysis(CFSR)data during the interval from 1988 to 2011.We analyzed these sources in detail at 6 km and obtained the main properties of their yearly variations.The DW1 source was found to present a weak seasonal variation in the lower latitudes(about±10°–15°).That is,the amplitudes of the DW1 sources were larger in the summer months than in the winter months,and DW1 presented semi-annual variation near the equator(±10°)such that the DW1 source was larger at the equinoxes than at the solstices.In addition,the SW2 source was symmetric and was stronger in the southern hemisphere than in the northern hemisphere.The SW2 source presented remarkable annual and semi-annual variation such that the amplitudes were largest during the March equinox months and larger during the June solstice months.In contrast,DE3 appeared mainly around the equatorial latitudes within about±30°.The DE3 source presented remarkable semiannual variation that was larger around the solstices than the equinoxes in the southern hemisphere,and it was opposite in the northern hemisphere.By HMD,we found that the tropospheric tides were primarily dominated by some leading propagating Hough modes,specifically,the(1,1),(2,3),and(3,3)modes;the influences of the other Hough modes were negligible.The consequences of an El Niño–Southern Oscillation modulation of tidal amplitudes for the energy and momentum budgets of the troposphere may now be expected to attract attention.In summary,the above yearly variations of the main tidal sources and the Hough coefficients demonstrate that an HMD

关键词： tropospheric tides Hough mode decomposition yearly variations

Influence of annual atmospheric tide asymmetry on annual anomalies of the ionospheric mean state

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Earth and Planetary Physics 2020年第5期4卷 429-435页

作者： ZhiPeng Ren weixing wan JianGang Xiong Xing Li Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China Beijing National Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of the Chinese Academy of SciencesBeijing 100049China School of Space and Environment Beihang UniversityBeijing 100083China Key Laboratory of Space Environment Monitoring and Information Processing Ministry of Industry and Information TechnologyBeijing 100083China

Through respectively adding June tide and December tide at the low boundary of the GCITEM-IGGCAS model (Global CoupledIonosphere–Thermosphere–Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences), we simulate theinfluence of atmospheric tide on the annual anomalies of the zonal mean state of the ionospheric electron density, and report that thetidal influence varies with latitude, altitude, and solar activity level. Compared with the density driven by the December tide, the June tidemainly increases lower ionospheric electron densities (below roughly the height of 200 km), and decreases electron densities in thehigher ionosphere (above the height of 200 km). In the low-latitude ionosphere, tides affect the equatorial ionization anomaly structure(EIA) in the relative difference of electron density, which suggests that tides affect the equatorial vertical E×B plasma drifts. Although thetide-driven annual anomalies do not vary significantly with the solar flux level in the lower ionosphere, in the higher ionosphere theannual anomalies generally decrease with solar activity.

关键词： ionospheric annual anomalies atmospheric tide ionosphere–atmosphere coupling

Chinese ionospheric investigations in 2016–2017

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Earth and Planetary Physics 2018年第2期2卷 89-111页

作者： LiBo Liu weixing wan Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Institutions of Earth Science Chinese Academy of SciencesBeijing 100029China Beijing National Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of the Chinese Academy of SciencesBeijing 100049China

After the release of the previous report to the Committee on Space Research(COSPAR) on progress achieved by Chinese scientists in ionospheric researches(Liu LB and wan WX, 2016), in the recent two years(2016–2017) many interesting new investigations into various ionospheric related issues have been completed. In this report, about 100 publications are summarized. The topics highlighted are as follows: Ionospheric space weather, ionospheric dynamics, ionospheric climatology and modelling, ionospheric irregularity and scintillation, Global Navigation Satellite System(GNSS) related ionospheric issues and other techniques, and radio wave propagation in the ionosphere. An outstanding feature is that more and more observations from the Meridional Project supported the ionospheric investigations.

关键词： ionosphere ionospheric storm space weather ionospheric dynamics irregularity

A local Martian crustal field model: Targeting the candidate landing site of the 2020 Chinese Mars Rover

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Earth and Planetary Physics 2020年第4期4卷 420-428页

作者： XinZhou Li ZhaoJin Rong JiaWei Gao Yong Wei Zhen Shi Tao Yu weixing wan Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth Science University of Chinese Academy of SciencesBeijing 100049China Beijing National Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China China University of Geosciences Wuhan 430074China

Unlike Earth,Mars lacks a global dipolar magnetic field but is dominated by patches of a remnant crustal magnetic field.In 2021,the Chinese Mars Rover will land on the surface of Mars and measure the surface magnetic field along a moving path within the possible landing region of 20°W-50°W,20°N-30°N.One scientific target of the Rover is to monitor the variation in surface remnant magnetic fields and reveal the source of the ionospheric current.An accurate local crustal field model is thus considered necessary as a field reference.Here we establish a local crust field model for the candidate landing site based on the joint magnetic field data set from Mars Global Explorer(MGS)and Mars Atmosphere and Volatile Evolution(MAVEN)data combined.The model is composed of 1,296 dipoles,which are set on three layers but at different buried depths.The application of the dipole model to the joint data set allowed us to calculate the optimal parameters of their dipoles.The calculated results demonstrate that our model has less fitting error than two other state-of-the art global crustal field models,which would indicate a more reasonable assessment of the surface crustal field from our model.

关键词： Mars remnant crustal field crustal field model dipole sources Chinese Mars mission

A simulation study of 630 nm and 557.7 nm airglow variations due to dissociative recombination and thermal electrons by high-power HF heating

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Earth and Planetary Physics 2017年第1期1卷 44-52页

作者： Tong Dang JiuHou Lei XianKang Dou weixing wan CAS Key Laboratory of Geospace Environment School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China Mengcheng National Geophysical Observatory University of Science and Technology of ChinaHefei 230026China Collaborative Innovation Center of Astronautical Science and Technology Harbin 150001China Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China

One of the important effects of the ionospheric modification by high-power waves is the airglow enhancement. Both the thermal electrons and the dissociation recombination contribute to generate the airglow emissions during HF heating. However, the relative importance of the airglow emission induced by dissociative recombination and thermal electrons has been rarely investigated. In this study, we carry out a simulation study on the airglow produced by high-power HF heating at nighttime associated with dissociative recombination and thermal electrons. SAMI2(Sami2 is Another Model of the Ionosphere) is employed to simulate the ionospheric variations during the HF heating. The main conclusions from this study are as follows:(1) For the airglow induced by dissociative recombination, both 630.0 nm and 557.7 nm emissions show a decrease at the heating wave reflection height during the heating period,while when the heating is turned off, an increase is shown at lower altitudes. The reduction of airglow during the heating is caused by the rapid increase of electron temperature and the diffusion of plasmas dominates the after-heating airglow enhancement.(2) 630.0 nm emission due to thermal electrons is greatly enhanced at the wave reflection height, indicating that thermal electrons play a major role in exciting 630.0 nm emission. For the 557.7 nm emission, the excitation threshold(4.17 e V) is too high for thermal electrons.(3) The combined effect of dissociative recombination and thermal electrons could be the possible reason for the observed X-mode(extraordinary mode) suppression of 630.0 nm airglow during O-mode(ordinary mode) enhancement.

关键词： airglow thermal electron dissociative recombination HF heating

Optimization of the Mars ionospheric radio occultation retrieval

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Earth and Planetary Physics 2018年第4期2卷 292-302页

作者： JunYi wang XinAn Yue Yong Wei weixing wan Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences Institutions of Earth Science Chinese Academy of Sciences College of Earth and Planetary Sciences University of Chinese Academy of Sciences

Electron density is a key parameter to characterize Martian ionospheric structure and dynamics. Based on the ephemeris and auxiliary information derived from the Spacecraft, Planet, Instruments, C-matrix, and Events(SPICE) toolkit, we calculated the bending angle of signal path from the frequency residuals measured by the Mars Express Radio Science Experiment(Ma RS) of the Mars Express(MEX) mission under the assumption of a spherically symmetric ionosphere. We stratified the ionosphere into layers and assumed a linear change of bending angle between layers, to derive profiles in radial distance of refractivity with the optimized parameters of upper integral limit of 4890 km and baseline correction boundary of 3690 km. Meanwhile, we also compared the retrieved electron density profiles between the frequency residuals of the single-frequency and differential Doppler of the dual-frequency. In total, ~640 electron density profiles of Martian ionosphere between April 2004 and April 2015 were retrieved successfully. There are 24 profiles identified manually that exhibit an additional sporadic layer occurrence below the normal two-layers. We also found that the peak altitude of this layer increases with the main peak altitude.

关键词： Mars ionosphere radio occultation electron density