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CN  10-1502/P

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Nighttime meridional neutral wind responses to SAPS simulated by the TIEGCM: a universal time effect
KeDeng Zhang, Hui Wang, WenBin Wang, Jing Liu, ShunRong Zhang, Cheng Sheng
Recently Published , doi: 10.26464/epp2021004
[Abstract](51) [FullText HTML](78) [PDF 9890KB](0)
The present work uses the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM), under geomagnetically disturbed conditions that are closely related to the southward interplanetary magnetic field (IMF), to investigate how the nighttime poleward wind (30°–50° magnetic latitude and 19–22 magnetic local time) responds to subauroral polarization streams (SAPS) that commence at different universal times (UTs). The SAPS effects on the poleward winds show a remarkable UT variation, with weaker magnitudes at 00 and 12 UT than at 06 and 18 UT. The strongest poleward wind emerges when SAPS commence at 06 UT, and the weakest poleward wind develops when SAPS occur at 00 UT. A diagnostic analysis of model results shows that the pressure gradient is more prominent for the developing of the poleward wind at 00 and 12 UT. Meanwhile, the effect of ion drag is important in the modulation of the poleward wind velocity at 06 and 18 UT. This is caused by the misalignment of the geomagnetic and geographic coordinate systems, resulting in a large component of ion drag in the geographically northward (southward) direction due to channel orientation of the SAPS at 06 and 18 UT (00 and 12 UT). The Coriolis force effect induced by westward winds maximizes (minimizes) when SAPS commence at 12 UT (00 UT). The centrifugal force due to the accelerated westward winds shows similar UT variations as the Coriolis force, but with an opposite effect.
Case study on stratospheric and mesospheric concentric gravity waves generated by deep convection
GuoChun Shi, Xiong Hu, ZhiGang Yao, WenJie Guo, MingChen Sun, XiaoYan Gong
Recently Published , doi: 10.26464/epp2021002
[Abstract](45) [FullText HTML](18) [PDF 13046KB](2)
Concentric gravity waves (CGWs) in the middle and upper atmosphere show wave-coupling processes between the lower atmosphere and the middle and upper atmosphere. In this research, we analyzed a case of CGWs detected simultaneously by the AIRS (Atmospheric Infrared Sounder) and the VIIRS/DNB (Day/Night Band of the Visible Infrared Imager Radiometer Suite) in the stratosphere and mesosphere. Results showed that gravity waves (GWs) were generated by the collocated Hurricane Bejisa on the island of Mauritius. The AIRS data showed arc-like phase fronts of GWs with horizontal wavelengths of 190 and 150 km at 21:08 coordinated universal time (UTC) on 1 January 2014 and at 10:00 UTC on 2 January 2014, whereas the DNB observed arced GWs with horizontal wavelengths of 60 and 150 km in the same geographic regions at 22:24 UTC. The characteristics of CGW parameters in the stratosphere (~40 km) and the mesosphere (~87 km), such as the vertical wavelength, intrinsic frequency, and intrinsic horizontal phase speed, were first derived together with the background winds from ERA5 reanalysis data and Horizontal Wind Model data through the dispersion relationship of GWs and the wind-filtering theory.
Characteristic analysis of layered PMSEs measured with different elevation angles at VHF based on an experimental case
ShuCan Ge, HaiLong Li, Bin Xu, Tong Xu, Lin Meng, MaoYan Wang, Abdel Hannachi, MengYan Zhu, Lina Broman, Safi Ullah, Abdur Rauf
Recently Published , doi: 10.26464/epp2021001
[Abstract](51) [FullText HTML](16) [PDF 810KB](2)
Polar Mesosphere Summer Echoes (PMSEs) are very strong radar echoes observed at altitudes near the polar summer mesopause. One of the essential properties of these radar echoes is that they can give useful diagnostic information about the physics of the scattering process. In this paper, the related characteristics of PMSEs measured with the European Incoherent SCATter Very High Frequency (EISCAT VHF) 224 MHz radar on 13–15 July 2010 are studied at different elevation angles from 78° to 90°. It is found that the PMSEs peak power and strongest PMSEs average power occur at the same elevation angles. Also interesting is that the strongest PMSEs occur at off-vertical angles when a PMSEs has a layered (multilayer) structure. And reflection may have more significant effects on PMSEs when there are double or multilayer PMSEs. Possible explanations regarding these observations are discussed.
Solar control of CO2 + ultraviolet doublet emission on Mars
ZiChuan Li, Jun Cui, Jing Li, XiaoShu Wu, JiaHao Zhong, FaYu Jiang
Recently Published , doi: 10.26464/epp2020064
[Abstract](160) [FullText HTML](44) [PDF 800KB](3)
The \begin{document}$ {\rm{CO}}_2^+$\end{document} ultraviolet doublet (UVD) emission near 289 nm is an important feature of dayside airglow emission from planetary upper atmospheres. In this study, we analyzed the brightness profiles of \begin{document}$ {\rm{CO}}_2^+$\end{document} UVD emission on Mars by using the extensive observations made by the Imaging Ultraviolet Spectrograph on board the recent Mars Atmosphere and Volatile Evolution spacecraft. Strong solar cycle and solar zenith angle variations in peak emission intensity and altitude were revealed by the data: (1) Both the peak intensity and altitude increase with increasing solar activity, and (2) the peak intensity decreases, whereas the peak altitude increases, with increasing solar zenith angle. These observations can be favorably interpreted by the solar-driven scenario combined with the fact that photoionization and photoelectron impact ionization are the two most important processes responsible for the production of excited-state \begin{document}$ {\rm{CO}}_2^+$\end{document} and consequently the intensity of \begin{document}$ {\rm{CO}}_2^+$\end{document} UVD emission. Despite this, we propose that an extra driver, presumably related to the complicated variation in the background atmosphere, such as the occurrence of global dust storms, is required to fully interpret the observations. In general, our analysis suggests that the \begin{document}$ {\rm{CO}}_2^+$\end{document} UVD emission is a useful diagnostic of the variability of the dayside Martian atmosphere under the influences of both internal and external drivers.
Numerical simulation of the propagation of electromagnetic waves in ionospheric irregularities
ChunHua Jiang, LeHui Wei, GuoBin Yang, Chen Zhou, ZhengYu Zhao
Recently Published , doi: 10.26464/epp2020059
[Abstract](78) [FullText HTML](29) [PDF 2699KB](1)
The characteristics of high-frequency (HF) electromagnetic (EM) wave propagation can be affected when EM waves propagate in the ionosphere. When ionospheric irregularities appear in the ionosphere, they can have a serious impact on the propagation of HF EM waves. In this study, the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation. First, a two-dimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere. A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities. Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities. In addition, corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities. The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde. Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere. This result was consistent with the ionosonde observations.
On the radar frequency dependence of polar mesosphere summer echoes
ShuCan Ge, HaiLong Li, Lin Meng, MaoYan Wang, Tong Xu, Safi Ullah, Abdur Rauf, Abdel Hannachid
Recently Published , doi: 10.26464/epp2020061
[Abstract](287) [FullText HTML](40) [PDF 2007KB](3)
Polar mesosphere summer echoes (PMSEs) are very strong radar echoes in the polar mesopause in local summer. Here we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipitation on modulated PMSEs by using PMSEs observations carried out by European Incoherent SCATter (EISCAT) heating equipment simultaneously with very high frequency (VHF) radar and ultra high frequency (UHF) radar on 12 July 2007. According to the experimental observations, the PMSEs occurrence rate at VHF was much higher than that at UHF, and the altitude of the PMSEs maximum observed at VHF was higher than that at UHF. Overlapping regions were observed by VHF radar between high energetic particle precipitation and the PMSEs. In addition, high-frequency heating had a very limited impact on PMSEs when the UHF electron density was enhanced because of energetic particle precipitation. In addition, an updated qualitative method was used to study the relationship between volume reflectivity and frequency. The volume reflectivity was found to be inversely proportional to the fourth power of radar frequency. The theoretical and experimental results provide a definitive data foundation for further analysis and investigation of the physical mechanism of PMSEs.
Refinement of Bouguer anomalies derived from the EGM2008 model, impact on gravimetric signatures in mountainous region: Case of Cameroon Volcanic Line, Central Africa
Paul Gautier Kamto, Cyrille Mezoue Adiang, Severin Nguiya, Joseph Kamguia, Loudi Yap
Recently Published , doi: 10.26464/epp2020065
[Abstract](223) [FullText HTML](14) [PDF 56590KB](19)
Global geopotential models have not included the very high frequencies of the Earth’s external gravity field. This is called omission error. This omission error becomes more important in mountainous areas (areas with highly variable topography). The work reported here consists in reducing the omission error in measurements of Bouguer gravity anomalies, by refining the global geopotential model EGM2008 using the spectral enhancement method. This method consists in computing the residual terrain effects and then coupling them to the gravimetric signal of the global geopotential model. To compute the residual terrain effects, we used the Residual Terrain Model (RTM) technique. To refine it required a reference surface (ETOPO1) developed up to degree 2190 (the maximum degree of the EGM2008 model) and a detailed elevation model (AW3D30). Computation was performed with the TC program of the GRAVSOFT package. The topography of the study area was assumed to have a constant density of 2670 kg/m3. For the inner and outer zones, the respective integration radii of 10 km and 200 km have been chosen. We obtained very important RTM values ranging from −53.59 to 34.79 mGal. These values were added to the gravity anomalies grid of the EGM2008 model to improve accuracy at high frequencies. On a part of the Cameroon Volcanic Line and its surroundings (mountainous area), we made a comparison between the residual Bouguer anomalies before and after refinement. We report differences ranging from −37.40 to 26.40 mGal. We conclude that the impact of omission error on gravimetric signatures is observed especially in areas with high variable topography, such as on the Cameroon Volcanic Line and around the localities of Takamanda, Essu, Dumbo, and Ngambe. This finding illustrates the great influence that topography has on accurate measurement of these gravity anomalies, and thus why topography must be taken into account. We can conclude that in preparing a global geopotential model, a high resolution DTM must be used to decrease the omission error: the degree of expansion has to increase in order to take the higher frequencies into account. The refined Bouguer anomalies grid presented here can be used in addition to terrestrial gravity anomalies in the study area, especially in mountainous areas where gravimetric data are very sparse or non-existent.
Proton belt variations traced back to Fengyun-1C satellite observations
ChunQin Wang, Zheng Chang, XiaoXin Zhang, GuoHong Shen, ShenYi Zhang, YueQiang Sun, JiaWei Li, Tao Jing, HuanXin Zhang, Ying Sun, BinQuan Zhang
Recently Published , doi: 10.26464/epp2020069
[Abstract](124) [FullText HTML](29) [PDF 3568KB](1)
We used historical data to trace trapped protons observed by the Fengyun-1C (FY-1C) satellite at low Earth orbits (~800 km) and chose data at 5–10 MeV, 10–40 MeV, 40–100 MeV, and ~100–300 MeV from 25 March to 18 April 2000 to analyze the proton variations. Only one isolated strong storm was associated with a solar proton event during this period, and there was no influence from previous proton variations. Complex dynamic phenomena of proton trapping and loss were affected by this disturbance differently depending on the energy and L location. The flux of 5–10 MeV protons increased and created new trapping with a maximum at L ~2.0, and the peak flux was significantly higher than that at the center of the South Atlantic Anomaly. However, at higher L, the flux showed obvious loss, with retreat of the outer boundary from L ~2.7 to L ~2.5. The increase in the 10–40 MeV proton flux was similar to that of the 5–10 MeV flux; however, the peak flux intensity was lower than that at the center of the South Atlantic Anomaly. The loss of the 10–40 MeV proton flux was closer to the Earth side, and the outer boundary was reduced from L ~2.3 to L ~2.25. For the higher energy protons of 40–100 MeV and 100–300 MeV, no new trapping was found. Loss of the 40–100 MeV protons was observed, and the outer boundary shifted from L ~2.0 to L ~1.9. Loss was not obvious for the 100–400 MeV protons, which were distributed within L < 1.8. New proton trapping was more likely to be created at lower energy in the region of solar proton injection by the strong magnetic storm, whereas loss occurred in a wide energy range and reduced the outer boundary on the Earth side. Similar dynamic changes were observed by the NOAA-15 satellite in the same period, but the FY-1C satellite observed more complex changes in lower energy protons. These results revealed that the dynamic behavior of protons with different L-shells was due to differences in the pitch angle. Possible mechanisms related to new trapping and loss are also discussed. These mechanisms are very important for understanding the behavior of the proton belt in the coming solar cycle.
Evidence of X-mode heating suppressing O-mode heating
Ting Feng, Chen Zhou, Xiang Wang, MoRan Liu, ZhengYu Zhao
Recently Published , doi: 10.26464/epp2020068
[Abstract](94) [FullText HTML](30) [PDF 2240KB](0)
In this study, we present three experiments carried out at the EISCAT (European Incoherent Scatter Scientific Association) heating facility on October 29 and 30, 2015. The results from the first experiment showed overshoot during the O-mode heating period. The second experiment, which used cold-start X-mode heating, showed the generation of parametric decay instability, whereas overshoot was not observed. The third experiment used power-stepped X-mode heating with noticeable O-mode wave leakage. Parametric decay instability and oscillating two-stream instability were generated at the O-mode reflection height without the overshoot effect, which implies suppression of the thermal parametric instability with X-mode heating. We propose that the electron temperature increased because X-mode heating below the upper hybrid height decreased the growth rate of the thermal parametric instability.
The diurnal transport of atmospheric water vapor during major dust storms on Mars based on the Mars Climate Database, version 5.3
Jing Li, ZhaoPeng Wu, Tao Li, Xi Zhang, Jun Cui
Recently Published , doi: 10.26464/epp2020062
[Abstract](293) [FullText HTML](33) [PDF 1723KB](1)
In recent studies of the Martian atmosphere, strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms, which provides strong evidence that the commonly recognized meridional transport process is driven by thermal tides. This process, when coupled with deep convection, could be an important part of the short-term atmospheric dynamics of water escape. However, the potential of this process to alter the horizontal distribution of moist air has not been systematically investigated. In this work, we conducted pre-research on the horizontal transport of water vapor associated with the migrating diurnal tide (DW1) at 50 Pa in the upper troposphere during major dust storms based on the Mars Climate Database (MCD) 5.3, a state-of-the-art database for Martian atmospheric research that has been validated as simulating the relevant short-period atmospheric dynamics well. We found westward-propagating diurnal patterns in the global water vapor front during nearly all the major dust storms from Martian years (MYs) 24 to 32. Statistical and correlation analyses showed that the diurnal transport of water vapor during global and A-season regional dust storms is dominated by the DW1. The effect of the tidal transport of water vapor varies with the types of dust storms in different seasons. During regional dust storms, the tidal transport induces only limited diurnal motion of the water vapor. However, the horizontal tidal wind tends to increase the abundance of daytime water vapor at mid- to low latitudes during the MY 28 southern summer global dust storm while decreasing it during the MY 25 southern spring global dust storm. The tidal transport process during these two global dust storms can induce opposite effects on water escape.
Preliminary experimental results by the prototype of Sanya Incoherent Scatter Radar
XinAn Yue, WeiXing Wan, Han Xiao, LingQi Zeng, ChangHai Ke, BaiQi Ning, Feng Ding, BiQiang Zhao, Lin Jin, Chen Li, MingYuan Li, JunYi Wang, HongLian Hao, Ning Zhang
Recently Published , doi: 10.26464/epp2020063
[Abstract](118) [FullText HTML](32) [PDF 43630KB](3)
In the past decades, the Incoherent Scatter Radar (ISR) has been demonstrated to be one of the most powerful instruments for ionosphere monitoring. The Institute of Geology and Geophysics at the Chinese Academy of Sciences was founded to build a state-of-the-art phased-array ISR at Sanya (18.3°N, 109.6°E), a low-latitude station on Hainan Island, named the Sanya ISR (SYISR). As a first step, a prototype radar system consisting of eight subarrays (SYISR-8) was built to reduce the technical risk of producing the entire large array. In this work, we have summarized the preliminary experimental results based on the SYISR-8. The amplitude and phase among 256 channels were first calibrated through an embedded internal monitoring network. The mean oscillation of the amplitude and phase after calibration were about 1 dB and 5°, respectively, which met the basic requirements. The beam directivity was confirmed by crossing screen of the International Space Station. The SYISR-8 was further used to detect the tropospheric wind profile and meteors. The derived winds were evaluated by comparison with independent radiosonde and balloon-based GPS measurements. The SYISR-8 was able to observe several typical meteor echoes, such as the meteor head echo, range-spread trail echo, and specular trail echo. These results confirmed the validity and reliability of the SYISR-8 system, thereby reducing the technical risk of producing the entire large array of the SYISR to some extent.
Sharpness of the paired 660-km discontinuity beneath the Izu-Bonin area
LiMing Wang, XiaoBo He
Recently Published , doi: 10.26464/epp2020067
[Abstract](138) [FullText HTML](39) [PDF 17245KB](4)
The 660-km discontinuity that separates the Earth's upper and lower mantle has primarily been attributed to phase changes in olivine and other minerals. Resolving the sharpness is essential for predicting the composition of the mantle and for understanding its dynamic effects. In this study, we used S-to-P conversions from the 660-km interface, termed S660P, arriving in the P-wave coda from one earthquake in the Izu–Bonin subduction zone recorded by stations in Alaska. The S660P signals were of high quality, providing us an unprecedented opportunity to resolve the sharpness of the discontinuity. Our study demonstrated, based on the impedance contrast given by the IASP91 model, that the discontinuity has a transitional thickness of ~5 km. In addition, we observed a prominent arrival right after the S660P, which was best explained by S-to-P conversions from a deeper discontinuity at a depth of ~720 km with a transitional thickness of ~20 km, termed S720P. The 720-km discontinuity is most likely the result of a phase transition from majoritic garnet to perovskite in the segregated oceanic crust (mainly the mid-oceanic ridge basalt composition) at the uppermost lower mantle beneath this area. The inferred phase changes are also consistent with predictions from mineral physics experiments.
The semiannual variation of transpolar arc incidence and its relationship to the Russell–McPherron effect
Tao Tang, Jun Yang, QuanQi Shi, AnMin Tian, Shi-Chen Bai, Alexander William Degeling, SuiYan Fu, JingXian Liu, Tong Shao, ZeYuan Sun
Recently Published , doi: 10.26464/epp2020066
[Abstract](124) [FullText HTML](40) [PDF 1137KB](0)
Earth’s aurora is a luminescent phenomenon generated by the interaction between magnetospheric precipitating particles and the upper atmosphere; it plays an important role in magnetosphere–ionosphere (M-I) coupling. The transpolar arc (TPA) is a discrete auroral arc distributed in the noon-midnight direction poleward of the auroral oval and connects the dayside to the nightside sectors of the auroral oval. Studying the seasonal variation of TPA events can help us better understand the long-term variation of the interaction between the solar wind, the magnetosphere, and M-I coupling. However, a statistical study of the seasonal variation of TPA incidence has not previously been carried out. In this paper, we have identified 532 TPA events from the IMAGE database (2000–2005) and the Polar database (1996–2002), and calculated the incidence of TPA events for different months. We find a semiannual variation in TPA incidence. Clear peaks in the incidence of TPAs occur in March and September; a less pronounced peak appears in November. We also examine seasonal variation in the northward interplanetary magnetic field (IMF) over the same time period. The intensity and occurrence rate of the northward IMF exhibit patterns similar to that of the TPA incidence. Having studied IMF Bz before TPA onset, we find that strong and steady northward IMF conditions are favorable for TPA formation. We suggest that the semiannual variation observed in TPA incidence may be related to the Russell–McPherron (R-M) effect due to the projection effect of the IMF By under northward IMF conditions.
On the loss mechanisms of radiation belt electron dropouts during the 12 September 2014 geomagnetic storm
Xin Ma, Zheng Xiang, BinBin Ni, Song Fu, Xing Cao, Man Hua, DeYu Guo, YingJie Guo, XuDong Gu, ZeYuan Liu, Qi Zhu
Recently Published , doi: 10.26464/epp2020060
[Abstract](258) [FullText HTML](40) [PDF 3711KB](0)
Radiation belt electron dropouts indicate electron flux decay to the background level during geomagnetic storms, which is commonly attributed to the effects of wave-induced pitch angle scattering and magnetopause shadowing. To investigate the loss mechanisms of radiation belt electron dropouts triggered by a solar wind dynamic pressure pulse event on 12 September 2014, we comprehensively analyzed the particle and wave measurements from Van Allen Probes. The dropout event was divided into three periods: before the storm, the initial phase of the storm, and the main phase of the storm. The electron pitch angle distributions (PADs) and electron flux dropouts during the initial and main phases of this storm were investigated, and the evolution of the radial profile of electron phase space density (PSD) and the (μ, K) dependence of electron PSD dropouts (where μ, K, and L* are the three adiabatic invariants) were analyzed. The energy-independent decay of electrons at L > 4.5 was accompanied by butterfly PADs, suggesting that the magnetopause shadowing process may be the major loss mechanism during the initial phase of the storm at L > 4.5. The features of electron dropouts and 90°-peaked PADs were observed only for >1 MeV electrons at L < 4, indicating that the wave-induced scattering effect may dominate the electron loss processes at the lower L-shell during the main phase of the storm. Evaluations of the (μ, K) dependence of electron PSD drops and calculations of the minimum electron resonant energies of H+-band electromagnetic ion cyclotron (EMIC) waves support the scenario that the observed PSD drop peaks around L* = 3.9 may be caused mainly by the scattering of EMIC waves, whereas the drop peaks around L* = 4.6 may result from a combination of EMIC wave scattering and outward radial diffusion.


Some features of effective radius and variance of dust particles in the numerical simulation of dust climate on Mars
Chi-Fong Wong, Kim-Chiu Chow, Kwing L. Chan, Jing Xiao, and Yemeng Wang
Accepted Articles , doi: 10.26464/epp2021005
[Abstract](10) [PDF](0)
Airborne dust is an important constituent in the Martian atmosphere because of its radiative interaction with the atmospheric circulation, and dust size is one crucial factor in determining this effect. In numerical modeling of the dust processes, description of the dust size is usually dependent on the choice of a particular size distribution function, or with fixed values of effective radius (ER) and effective variance (EV) though they are variable in reality. In this work, analytical expressions have been derived to specify ER and EV for N-bin dust schemes based on the model calculated dust mixing ratio. Numerical simulations based on this approach thus consider the effects of variable ER on the atmospheric radiation and their interaction. The results have revealed some interesting features of the dust distribution parameters such as the seasonal and spatial variation of ER and EV, which are generally consistent with some previous observational and modeling studies. Compared with the usual approach of using fixed ER, simulation results with the present approach suggest that the variability of ER can have significant effect on the simulated thermal field of the Martian atmosphere.
Wide-field aurora imager onboard Fengyun satellite: Data products and validation
GuangXing Ding, JiaWei Li, XiaoXin Zhang, Fei He, LingPing He, KeFei Song, Liang Sun, Shuang Dai, ShiJie Liu, Bo Chen, Chao Yu, XiuQing Hu, SongYan Gu, ZhongDong Yang, Peng Zhang
Accepted Articles , doi: 10.26464/epp2021003
[Abstract](11) [PDF](0)
New observations of auroras based on the wide-field aurora imager (WAI) onboard Fengyun-3D (FY-3D) satellite are exhibited in this paper. Validity of the WAI data is analyzed by comparing auroral boundaries derived from WAI observations with results obtained from data collected by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) aboard the Defense Meteorological Satellite Program (DMSP F18). Dynamic variations of the aurora with the solar wind, interplanetary magnetic field (IMF) parameters, and the SYM-H index are also investigated. The comparison of auroral boundaries indicates that the WAI data are morphologically valid and suitable to the study of auroral dynamics. Effective responses to solar wind parameters indicate that the WAI data can be useful to monitor and predict the Earth’s space weather. Since the configuration of aurora is a good indicator of the solar wind-magnetosphere-ionosphere (SW-M-I) coupling system, and can reflect the disturbance of the space environment, the WAI will provide important data to help us to study the physical processes in space.
Dielectric Permittivity for Dusty Plasma in the Earth's Mesosphere
Hui Li and Jian Wu
Accepted Articles , doi: 10.26464/epp2021006
[Abstract](11) [PDF](2)
This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere. We give expressions for the complex dielectric permittivity of dusty plasma, taking into account the effects of the dust charging process and magnetic field. We discuss the dielectric permittivity of dusty plasma in several cases, such as high frequency approximation, parallel propagation in MF/HF band, and effects of plasma movement. Finally, the expressions are employed to study the phenomenon of radar echoes from the polar summer mesosphere. It is illustrated that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω-4 and to the production of charged dust number density, which coincides with radar echo measurements in the mesosphere.

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Influence of annual atmospheric tide asymmetry on annual anomalies of the ionospheric mean state
ZhiPeng Ren, WeiXing Wan, JianGang Xiong, Xing Li
2020, 4(5): 429 -435   doi: 10.26464/epp2020041
Through respectively adding June tide and December tide at the low boundary of the GCITEM-IGGCAS model (Global Coupled Ionosphere–Thermosphere–Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences), we simulate the influence of atmospheric tide on the annual anomalies of the zonal mean state of the ionospheric electron density, and report that the tidal influence varies with latitude, altitude, and solar activity level. Compared with the density driven by the December tide, the June tide mainly increases lower ionospheric electron densities (below roughly the height of 200 km), and decreases electron densities in the higher 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 the tide-driven annual anomalies do not vary significantly with the solar flux level in the lower ionosphere, in the higher ionosphere the annual anomalies generally decrease with solar activity.
Wavenumber-4 spectral component extracted from TIMED/SABER observations
Xing Li, WeiXing Wan, JinBin Cao, ZhiPeng Ren
2020, 4(5): 436 -448   doi: 10.26464/epp2020040
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.
The source of tropospheric tides
Xing Li, WeiXing Wan, JinBin Cao, ZhiPeng Ren
2020, 4(5): 449 -460   doi: 10.26464/epp2020049
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 semi-annual 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 analysis can be used to investigate the tropospheric tides.
Inertial gravity waves observed by a Doppler wind LiDAR and their possible sources
XiangHui Xue, DongSong Sun, HaiYun Xia, XianKang Dou
2020, 4(5): 461 -471   doi: 10.26464/epp2020039
In this paper, we use wind observations by a Doppler wind LiDAR near Delingha (37.4°N, 97.4°E), Qinghai, Northwestern China to study the characteristics of inertial gravity waves in the stratosphere. We focus on 10–12 December 2013, a particularly interesting case study. Most of the time, the inertial gravity waves extracted from the LiDAR measurements were stationary with vertical wavelengths of about 9–11 km and horizontal wavelengths of about 800–1000 km. However, for parts of the observational period in this case study, a hodograph analysis indicates that different inertial gravity wave propagation features were present at lower and upper altitudes. In the middle and upper stratosphere (~30–50 km), the waves propagated downward, especially during a period of stronger winds, and to the northwest–southeast. In the lower stratosphere and upper troposphere (~10–20 km), however, waves with upward propagation and northeast–southwest orientation were dominant. By taking into account reanalysis data and satellite observations, we have confirmed the presence of different wave patterns in the lower and upper stratosphere during this part of the observational period. The combined data sets suggest that the different wave patterns at lower and upper height levels are likely to have been associated with the presence of lower and upper stratospheric jet streams.
Reponses of middle atmospheric circulation to the 2009 major sudden stratospheric warming
ShengYang Gu, Xin Hou, JiaHui Qi, KeMin TengChen, XianKang Dou
2020, 4(5): 472 -478   doi: 10.26464/epp2020046
In this research, the roles of gravity waves and planetary waves in the change to middle atmospheric residual circulation during a sudden stratospheric warming period are differentiated and depicted separately by adopting the downward control principle. Our analysis shows clear anomalous poleward residual circulation patterns from the equator to high latitudes in the lower winter stratosphere. At the same time, upward mean flows are identified at high latitudes of the winter upper stratosphere and mesosphere, which turn equatorward in the mesosphere and reach as far as the tropical region, and consequently the extratropical region in the summer hemisphere. The downward control principle shows that anomalous mesospheric residual circulation patterns, including interhemispheric coupling, are solely caused by the change in gravity wave forcing resulting from the reversal of the winter stratospheric zonal wind. Nevertheless, both planetary waves and gravity waves are important to variations in the winter stratospheric circulation, but with opposite effects.
Diurnal variability of the planetary boundary layer height estimated from radiosonde data
Jie Gu, YeHui Zhang, Na Yang, Rui Wang
2020, 4(5): 479 -492   doi: 10.26464/epp2020042
Diurnal variations in the planetary boundary layer height (PBLH) at different latitudes over different surface characteristics are described, based on 45 years (1973−2017) of radiosonde observations. The PBLH is determined from the radiosonde data by the bulk Richardson number (BRN) method and verified by the parcel method and the potential temperature gradient method. In general, the BRN method is able to represent the height of the convective boundary layer (BL) and neutral residual layer cases but has relatively large uncertainty in the stable BL cases. The diurnal cycle of the PBLH over land is quite different from the cycle over ocean, as are their seasonal variations. For stations over land, the PBLH shows an apparent diurnal cycle, with a distinct maximum around 15:00 LT, and seasonal variation, with higher values in summer. Compared with the PBLH over land, over oceans the PBLH diurnal cycles are quite mild, the PBLHs are much lower, and the seasonal changes are less pronounced. The seasonal variations in the median PBLH diurnal cycle are positively correlated with the near-surface temperature and negatively correlated with the near-surface relative humidity. Finally, although at most latitudes the daytime PBLH exhibits, over these 45 years, a statistically significant increasing trend at most hours between 12:00 LT and 18:00 LT over both land and ocean, there is no significant trend over either land or ocean in the nighttime PBLH for almost all the studied latitudes.
Comparison of stratospheric evolution during the major sudden stratospheric warming events in 2018 and 2019
Zheng Ma, Yun Gong, ShaoDong Zhang, JiaHui Luo, QiHou Zhou, ChunMing Huang, KaiMing Huang
2020, 4(5): 493 -503   doi: 10.26464/epp2020044
Using Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) data in the northern hemisphere at the 10 hPa level, we compared the stratospheric evolution of temperature and geopotential height during two major sudden stratosphere warming events (SSWs) that occurred in the Arctic winter of 2018 and 2019. In the prewarming period, poleward temperature-enhanced regions were mainly located around 120°E with a displaced vortex and around 120°E and 60°W with splitting vortices. The evolution of geopotential height indicated that these temperature-enhanced regions were both on the western side of high-latitude anticyclones. In the postwarming period, the polar vortex turned from splitting to displacement in the 2018 SSW but from displacement to splitting in the 2019 SSW. Both transitions were observed over the Atlantic region, which may have been caused by anticyclones moving through the polar region. Our findings revealed that the evolution of the anticyclone is important during SSWs and is closely related to temperature-enhanced regions in the prewarming periods and to transitions of the polar vortices in postwarming periods.
Global static stability and its relation to gravity waves in the middle atmosphere
Xiao Liu, JiYao Xu, Jia Yue
2020, 4(5): 504 -512   doi: 10.26464/epp2020047
The global atmospheric static stability (N2) in the middle atmosphere and its relation to gravity waves (GWs) were investigated by using the temperature profiles measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument from 2002 to 2018. At low latitudes, a layer with enhanced N2 occurs at an altitude of ~20 km and exhibits annual oscillations caused by tropopause inversion layers. Above an altitude of ~70 km, enhanced N2 exhibits semiannual oscillations at low latitudes caused by the mesosphere inversion layers and annual oscillations at high latitudes resulting from the downward shift of the summer mesopause. The correlation coefficients between N2 and GW amplitudes can be larger than 0.8 at latitudes poleward of ~40°N/S. This observation provides factual evidence that a large N2 supports large-amplitude GWs and indicates that N2 plays a dominant role in maintaining GWs at least at high latitudes of the middle atmosphere. This evidence also partially explains the previous results regarding the phase changes of annual oscillations of GWs at high latitudes.
Effect of lateral heterogeneity on 2-D Rayleigh wave ZH ratio sensitivity kernels based on the adjoint method: Synthetic and inversion examples
Ting Lei, HuaJian Yao, Chao Zhang
2020, 4(5): 513 -522   doi: 10.26464/epp2020050
The ratio between vertical and radial amplitudes of Rayleigh waves (hereafter, the Rayleigh wave ZH ratio) is an important parameter used to constrain structures beneath seismic stations. Some previous studies have explored crust and upper mantle structures by joint inversion of the Rayleigh wave ZH ratio and surface wave dispersion. However, all these studies have used a 1-D depth sensitivity kernel, and this kernel may lack precision when the structure varies a great deal laterally. Here, we present a systematic investigation of the two-dimensional (2-D) Rayleigh wave ZH ratio kernel based on the adjoint-wavefield method and perform two synthetic tests using the new kernel. The 2-D ZH ratio kernel is consistent with the traditional 1-D sensitivity kernel but has an asymmetric pattern with a preferred orientation toward the source. The predominant effect caused by heterogeneity can clearly be seen from kernels calculated from models with 2-D heterogeneities, which confirms the necessity of using the new 2-D kernel in some complex regions. Inversion tests using synthetic data show that the 2-D ZH ratio kernel has the potential to resolve small anomalies as well as complex lateral structures.
Analysis of the role of branching angle in the dynamic rupture process on a 3-D branching fault system
JingXing Fang, Feng Qian, HaiMing Zhang
2020, 4(5): 523 -531   doi: 10.26464/epp2020043
The fault branching phenomenon, which may heavily influence the patterns of rupture propagation in fault systems, is one of the geometric complexities of fault systems that is widely observed in nature. In this study, we investigate the effect of the branching angle on the rupture inclination and the interaction between branch planes in two-fork branching fault systems by numerical simulation and theoretical analysis based on Mohr’s circle. A friction law dependent on normal stress is used, and special attention is paid to studying how ruptures on the upper and lower branch planes affect the stress and rupture on each other separately. The results show that the two branch planes affect each other in different patterns and that the intensity of the effect changes with the branching angle. The rupture of the lower branch plane has a negative effect on the rupture of the upper branch plane in the case of a small branching angle but has almost no negative effect in the case of a large branching angle. The rupture of the upper branch plane, however, suppresses the rupture of the lower branch plane regardless of whether the branching angle is large or small.
Monitoring of velocity changes based on seismic ambient noise: A brief review and perspective
Qing-Yu Wang, HuaJian Yao
2020, 4(5): 532 -542   doi: 10.26464/epp2020048
Over the past two decades, the development of the ambient noise cross-correlation technology has spawned the exploration of underground structures. In addition, ambient noise-based monitoring has emerged because of the feasibility of reconstructing the continuous Green’s functions. Investigating the physical properties of a subsurface medium by tracking changes in seismic wave velocity that do not depend on the occurrence of earthquakes or the continuity of artificial sources dramatically increases the possibility of researching the evolution of crustal deformation. In this article, we outline some state-of-the-art techniques for noise-based monitoring, including moving-window cross-spectral analysis, the stretching method, dynamic time wrapping, wavelet cross-spectrum analysis, and a combination of these measurement methods, with either a Bayesian least-squares inversion or the Bayesian Markov chain Monte Carlo method. We briefly state the principles underlying the different methods and their pros and cons. By elaborating on some typical noise-based monitoring applications, we show how this technique can be widely applied in different scenarios and adapted to multiples scales. We list classical applications, such as following earthquake-related co- and postseismic velocity changes, forecasting volcanic eruptions, and tracking external environmental forcing-generated transient changes. By monitoring cases having different targets at different scales, we point out the applicability of this technology for disaster prediction and early warning of small-scale reservoirs, landslides, and so forth. Finally, we conclude with some possible developments of noise-based monitoring at present and summarize some prospective research directions. To improve the temporal and spatial resolution of passive-source noise monitoring, we propose integrating different methods and seismic sources. Further interdisciplinary collaboration is indispensable for comprehensively interpreting the observed changes.
show more results
Corotating drift-bounce resonance of plasmaspheric electron with poloidal ULF waves
Qiu-Gang Zong, YongFu Wang, Jie Ren, XuZhi Zhou, SuiYan Fu, Robert Rankin, Hui Zhang
2017, 1(1): 2-12   doi: 10.26464/epp2017002
Ambient noise surface wave tomography of marginal seas in east Asia
Qing Wang, XiaoDong Song, JianYe Ren
2017, 1(1): 13-25   doi: 10.26464/epp2017003
A seismic model for crustal structure in North China Craton
TianYu Zheng, YongHong Duan, WeiWei Xu, YinShuang Ai
2017, 1(1): 26-34   doi: 10.26464/epp2017004
Thermal structures of the Pacific lithosphere from magnetic anomaly inversion
Chun-Feng Li, Jian Wang
2018, 2(1): 52-66   doi: 10.26464/epp2018005
The first joint experimental results between SURA and CSES
XueMin Zhang, Vladimir Frolov, ShuFan Zhao, Chen Zhou, YaLu Wang, Alexander Ryabov, DuLin Zhai
2018, 2(6): 527-537   doi: 10.26464/epp2018051
A brief review of equatorial ionization anomaly and ionospheric irregularities
Nanan Balan, LiBo Liu, HuiJun Le
2018, 2(4): 257-275   doi: 10.26464/epp2018025
Different earthquake patterns for two neighboring fault segments within the Haiyuan Fault zone
ZhiKun Ren, ZhuQi Zhang, PeiZhen Zhang
2018, 2(1): 67-73   doi: 10.26464/epp2018006
Radiation belt electron scattering by whistler-mode chorus in the Jovian magnetosphere: Importance of ambient and wave parameters
BinBin Ni, Jing Huang, YaSong Ge, Jun Cui, Yong Wei, XuDong Gu, Song Fu, Zheng Xiang, ZhengYu Zhao
2018, 2(1): 1-14   doi: 10.26464/epp2018001
Exact local refinement using Fourier interpolation for nonuniform-grid modeling
JinHai Zhang, ZhenXing Yao
2017, 1(1): 58-62   doi: 10.26464/epp2017008
Monitoring the geospace response to the Great American Solar Eclipse on 21 August 2017
Shun-Rong Zhang, Philip J. Erickson, Larisa P. Goncharenko, Anthea J. Coster, Nathaniel A. Frissell
2017, 1(1): 72-76   doi: 10.26464/epp2017011

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