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China’s Mars exploration mission has stimulated tremendous interest in planetary science exploration recently. To propose potential scientific research projects, this study presents a concept simulation for the measurement of Martian atmospheric winds using the Doppler Michelson interferometry technique. The simulation is based on the satellite instrument initially designed for the Dynamic Atmosphere Mars Observer (DYNAMO) project to measure vertical profiles of winds from the 1.27 μm airglow observations in the Martian atmosphere. A comprehensive DYNAMO measurement simulation forward model based on an orbit submodel, an atmospheric background field submodel, and an instrument submodel is developed using the Michelson equation. The simulated interferogram signal over the field of view (FOV) calculated by the forward model is associated with the filter transmittance function, column emission rate of airglow, wind velocity, temperature, and the Michelson phase. The agreement between the derived atmospheric signals from the simulated interferogram without altitude inversion and the input parameters used to initiate the forward model confirms the validity of the forward model.

Based on the electron density, field‐aligned currents (FACs) and ion drift velocity data from the Swarm‐A satellite during 2013–2018, we investigate the features of the high‐latitude trough in the Southern Hemisphere. The results show that the high‐latitude trough in the Southern Hemisphere is a persistent postmidnight feature in winter. It is observed mainly in the eastern longitudes under low solar activity conditions and in a smaller longitudinal range under high solar activity conditions. The high‐latitude trough moves to higher latitudes at later local times, which is more obvious under low solar activity conditions. We also find that the features of FACs and ion drift velocity distribution in the high‐latitude trough region depend on longitude. In the longitude sector of 0°–70°E, the high‐latitude trough positions are always located at the poleward boundary of the downward FAC region, and collocated with the convection reversal boundary in the postmidnight region. In the longitude sector of 80°–130°E, the high‐latitude trough positions are located at the poleward boundary of the downward FAC region in the midnight region and at the strong westward or antisunward ion flow region in the postmidnight region. It is suggested that the high‐latitude trough formation and evolution is possibly associated with downward FACs, flow stagnation in the convection reversal boundary, and westward or antisunward ion flow. Ionospheric troughs are depletions of the nighttime Fregion plasma density around the auroral and polar regions. The presence of the trough has a significant impact on the radio transmission. There are two types of troughs: the midlatitude trough and the high‐latitude trough. The midlatitude trough locates on the equatorward side of the auroral oval, and the high‐latitude trough locates within the auroral oval or polar cap. The features and formation mechanisms of the high‐latitude trough in the Southern Hemisphere are not yet clear. This study uses a new multiparameter data set gathered by the Swarm‐A satellite to find out the features and formation mechanisms of the high‐latitude trough in the Southern Hemisphere. We found that the high‐latitude trough in the Southern Hemisphere is a persistent postmidnight feature in winter. It is observed mainly in the eastern longitudes. The features of FACs and ion drift velocity distribution in the high‐latitude trough region depend on longitude. The formation and evolution of the high‐latitude trough is suggested to be associated with downward FACs, flow stagnation in the convection reversal boundary, and westward or antisunward ion flow. The high‐latitude trough is a persistent postmidnight feature in winter in the Southern HemisphereThe high‐latitude trough is observed mainly in the eastern longitudesThere is a longitude dependence of features of FACs and ion drift velocity distribution in the high‐latitude trough region

With an improved method for retrieving the equatorial Fregion irregularities (EFIs) from radio occultation measurements, a huge amount of S4 index profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites is employed to study the solar cycle variation of global EFIs during the period of 2007 to 2017. This full solar cycle data show that impacts of the solar activity on the occurrence rates and heights of EFIs are notable and complex. The occurrence rates of EFIs at higher altitude (greater than 500 km) increase with increasing the solar activity. The mean heights ( h~) and heights standard deviation (σh) of EFIs at higher altitudes do not show clearly the solar activity dependence. On the other hand, the occurrence rates of EFIs at entire altitudes (from 150 to 800 km) do not have clear relation with the solar activity. The h~and σhof EFIs at entire altitudes increase with increasing the solar activity. Moreover, the dependence of the occurrence rates of EFIs on the solar activity are the strongest in the equinoxes, weaker in winter and weakest in summer. The electric fields and corresponding seasonal variation can account for the EFIs occurrence and height variation versus solar activities, and the EFIs at low altitudes seem to be related to the seedassociated with atmospheric gravity wave. The performance of EFIs changes with solar activity is complex. The solar dependence of EFIs seems to be inconsistent when using different observation, i.e. the ground‐base observation indicates no solar dependence, but space‐based observation indicates very good solar dependence. We suppose that this may be due to the fact that EFI at different altitudes is has different solar dependence. For the first time in this article, we have distinguished the information of the height of the EFIs. This is the great advantage of the COSMIC occultation data. After distinguishing the heights, it was found that the occurrence of EFIs above 500 km was well correlated with solar activity, and the correlation between the entire height of EFIs and solar activity was weak. The results of this study are a good explanation of the reasons for the inconsistency of the previous researcher's EFIs solar dependence study. We use COSMIC occultation data statistical studies on climatological characteristics of the global EIFsThe occurrence of EFIs above 500 km was well correlated with solar activityThe correlation between the entire height of EFIs and solar activity was weak

A new method for estimating the equatorial plasma bubbles (EPBs) motions from airglow emission all‐sky images is presented in this paper. This method, which is called cloud motion wind(CMW) and widely used in satellite observation of wind, could reasonably derive zonal and meridional velocity vectors of EPBs drift by tracking a series of successive airglow images. Airglow emission images data are available from all‐sky airglow camera in Hainan Fuke (19.5°N, 109.2°E) supported by China Meridional Project, which can receive the 630.0 nm emission from ionosphere Fregion at low latitudes to observe plasma bubbles. A series of pretreatment technology is utilized to preprocess the raw observation. Then the regions of plasma bubble extracted from the images are divided into several small tracing windows, and each tracing window can find a target window in the searching area in following image, which is considered as the position tracing window moved to. According to this, velocity of each tracing window was calculated by CMW. The maximum correlation coefficient is adopted to analyze the velocity of plasma bubbles due to its better performance than histogram of oriented gradient. All‐sky images from Hainan Fuke, an example on 17 September 2014, are analyzed to investigate the plasma bubble drift velocities using CMW. For comparison and validation, EPBs motions obtained from three traditional methods are also investigated. The advantages and disadvantages of using CMW are discussed. The results of CMW are compared with slant total electron contents data and show a good consistency, but some errors are also discussed. The advantages of our method are as follows. First, CMW can obtain the velocity of different parts in EPB. Second, the result of CMW has a relatively good stability. The disadvantage of CMW is that the computational complexity is sometimes large, because self‐adaptive method is used and this process involves looping operations. The result of CMW shows a good consistency with GPS STEC data, which means that the results of CMW are generally reliable. Equatorial plasma bubbles velocity is derived by cloud motion wind (CMW) technology by tracking a series of successive airglow imagesCMW can obtain the velocity of different parts in EPBResults of CMW are compared with STEC data and show a good consistency, but some errors are also discussed

In previous studies, various physical parameters, such as vertical wind shear null, vertical ion velocity null (IVN), and maximum gradient of vertical ion velocity, have been used as an indicator of Es layer height in light of the wind shear theory. Using a numerical Es layer model, we investigated which parameter represents the height of Es layer over Wuhan (114.4°E, 30.5°N) most precisely. The simulation results show that the height of Es layer above 110 km depends most strongly on the height of vertical IVN. However, below 110 km, the height of vertical IVN does not always agree with the height of Es layer. The analysis of simulation results suggests that the vertical gradient of the ratio of the ion‐neutral collision frequency (νi) to the ion gyrofrequency (ωi) affects the Es layer formation at lower altitudes (below 110 km). We also examined the effect of electric fields on the height and intensity of Es layers over Wuhan. It is found that eastward/upward electric fields can lift the Es layer height and reduce the Es layer intensity. Above 110 km, the height of Es layer agrees well with the height of the vertical ion velocity nullMid‐latitude Es layer density and height can be modulated by the electric fieldThe vertical gradient of the ratio of the ion‐neutral collision frequency (νi${\nu }_{i}$) to the ion gyrofrequency (ωi${\omega }_{i}$) also promotes Es layer formation Above 110 km, the height of Es layer agrees well with the height of the vertical ion velocity null Mid‐latitude Es layer density and height can be modulated by the electric field The vertical gradient of the ratio of the ion‐neutral collision frequency (νi${\nu }_{i}$) to the ion gyrofrequency (ωi${\omega }_{i}$) also promotes Es layer formation

A new method for estimating daily averaged peak height of the OH airglow layer from a ground‐based meteor radar (MR) and a Fabry‐Perot interferometer (FPI) is presented. The first results are derived from 4 year simultaneous measurements of winds by a MR and a FPI at two adjacent stations over center China and are compared with observations from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument. The OH airglow peak heights, which are derived by using correlation analysis between winds of the FPI and MR, are found to generally peak at an altitude of 87 km and frequently varied between 80 km and 90 km day to day. In comparison with SABER OH 1.6 μm observations, reasonable similarity of airglow peak heights is found, and rapid day‐to‐day variations are also pronounced. Lomb‐Scargle analysis is used to determine cycles of temporal variations of airglow peak heights, and there are obvious periodic variations both in our airglow peak heights and in the satellite observations. In addition to the annual, semiannual, monthly, and three monthly variations, the shorter time variations, e.g., day‐to‐day and several days' variations, are also conspicuous. The day‐to‐day variations of airglow height obviously could reduce observation accuracy and lead to some deviations in FPI measurements. These FPI wind deviations arising from airglow height variations are also estimated to be about 3–5 m/s from 2011 to 2015, with strong positive correlation with airglow peak height variation. More attention should be paid to the wind deviations associated with airglow height variation when using and interpreting winds measured by FPI. Airglow heights are derived by simultaneous observation of MR and FPI. It provides a chance for continuous studying their temporal variationIn addition to the long‐term variations, the day‐to‐day variations are also conspicuousFPI wind difference arising from height variations is about 3–5 m/s. One should pay attention to this difference when using FPI winds

In this paper we presented two typical global 6-day planetary wave oscillations occurring in sporadic Elayers. By analyzing the foEstime series observed from several ionosonde stations on the basis of the methods suggested by Haldoupis and Pancheva (2002), we computed estimates for the PW propagation direction, zonal wave number and phase velocity. We obtained results that the 6-day PW, with zonal wave number about 1, propagates westward, which are in agreement with those reported from radar and satellite neutral wind MLT measurements. The results provide experimental evidence for a close relationship between PWs and midlatitude Es. In addition, the study proves the validity of Esobservations measured routinely and rather reliably with a dense global network of digital ionosondes used as an alternative means of studying large-scale neutral atmospheric dynamics in the MLT region.

Quasi 6-day oscillations in Esoccurrence were observed to occur in relation with planetary wave activity at Wuhan, China (30.6°N, 114.5°E). Wavelet analysis of Esoccurrence time series revealed that a strong 5- to 7-day oscillation was present during the period from about day 120 to 137 of 2003. The same quasi 6-day planetary wave oscillation was also found to dominate the spectrum of concurrent wind data measured in the 80- to 100-km region by a meteor radar, in agreement with the Esoccurrence. There is also a great deal of similarity between the 5- to 7-day band-pass filtered waveforms of Esoccurrence and the wind data. By estimating the wave phase changes with altitude, the quasi 6-day PW in the zonal wind was found to be in phase with the sporadic Elayer critical frequency, foEs, at about 115 km, close to the observed Esheight. The quasi 6-day PW modulation was also present in the amplitude of the 12-h and 24-h periodicities which existed in the foEstime series. The present results provide new evidence in favor of a planetary wave indirect role on Esformation through the modulation of tides, which in line with previous studies by Haldoupis and Pancheva (2002), and Pancheva et al.(2003).

Sporadic E (Es) layers are known for their layered structures with enhanced electron density. Recently, some scientists have studied the relationship between the occurrence rate and intensity of the Es layer in the global distribution. However, the relationship between the Es layer parameters (Es layer occurrence rate, Es layer intensity, Es layer thickness) in the vertical direction seems to be ignored to date. This paper highlights the vertical profiles of the occurrence rate, intensity, and thickness of the Es layers by using scintillation index (S4) from FORMOSAT‐3/COSMIC satellites from July 2007 to March 2015. The results show that there are some persistent differences between the occurrence rate, intensity, and thickness of the Es layers in the vertical profiles, which is different from their general similarity in the latitude distribution. It is found that the Es layer occurrence rate has a maximum value at ∼102 km altitude, but the Es layer intensity and Es layer thickness reach their maximum at an altitude of ∼110 km. Besides, the intensity and thickness of the Es layer exhibit a high linear relationship, which suggests that the larger electron density of the Es layer, the thicker its thickness. The Horizontal Wind Model (HWM14) indicates that the latitudinal variations in Es layers parameters are highly coincident with the zonal wind shear. However, the altitudinal variations in Es layers parameters do not agree well with the zonal wind shear. The vertical variations of the occurrence rate, intensity, and thickness of the Sporadic E (Es) layers are presented in detailTheir vertical variations exist obvious discrepancies, which is different from their high similarity in latitudeCompared with the Es layer occurrence rate, the Es layer intensity can better reflect the evolution of the Es layer in vertical direction The vertical variations of the occurrence rate, intensity, and thickness of the Sporadic E (Es) layers are presented in detail Their vertical variations exist obvious discrepancies, which is different from their high similarity in latitude Compared with the Es layer occurrence rate, the Es layer intensity can better reflect the evolution of the Es layer in vertical direction

This work statistically analyzed the characteristics of the summer descending sporadic E layers (Es) recorded at four Chinese ionospheric sounding stations of Sanya (109.4°E, 18.3°N, and I: 24.1°), Wuhan (114.4°E, 30.5°N, and I: 45.5°), Beijing (116.2°E, 40.3°N, and I: 58.7°), Mohe (122.5°E, 52.0°N, and I: 69.6°), and simulated the vertical ion convergence derived from the Horizontal Wind Model (HWM14) for the period from June 1, 2014 to August 31, 2017. Both observations and simulations show that a daytime Es layer starting at ∼120 km in the morning descends to ∼100 km in the afternoon. In addition, the descending rate of the Es layer has obvious altitude and latitude dependence. The Es layer descends faster (∼2.1 km/h) at higher altitudes (above 110 km), and meanwhile, it descends relatively slowly (∼1.5 km/h) at low altitudes (below 110 km). The mean descending rate (∼1.5–1.8 km/h) of the Es layers gradually increases from Sanya to Mohe. It is undoubtedly that the wind shear convergence nodes controlled by the atmospheric tides can drive the Es layer to move downwards. However, the simulation results in this paper show that the wind shear convergence nodes and the Es layer traces do not overlap completely, especially in the vertical direction, which suggests that wind shear cannot fully explain the details of Es layer evolution. We should pay attention to the combined effect of wind shear and metallic ion density in future research, especially in the details of the evolution of Es layer in the vertical direction. Both observations and simulations show that the Es layer traces and wind shear convergence nodes have a downward movement trend, which is mainly controlled by the atmosphere tidesThe Es layer’s descending rates increase with altitude and latitude from Sanya to MoheThe Es layer traces observed by the ionosondes and the wind shear convergence nodes derived from the HWM14 model do not completely overlap, especially in the vertical direction Both observations and simulations show that the Es layer traces and wind shear convergence nodes have a downward movement trend, which is mainly controlled by the atmosphere tides The Es layer’s descending rates increase with altitude and latitude from Sanya to Mohe The Es layer traces observed by the ionosondes and the wind shear convergence nodes derived from the HWM14 model do not completely overlap, especially in the vertical direction

Sudden stratospheric warming (SSW) events in Northern Hemisphere winter atmosphere play a significant effect on large ionospheric disturbances. Nevertheless, the SSW effects on small‐scale structure in ionosphere, that is, the ionospheric Flayer irregularities, are generally lack of understanding. This work carefully studied the equatorial Flayer scintillation during the SSW event extending from 4 January to 5 February in 2013 by using the data of COSMIC/FORMOSAT‐3 (a Constellation Observing System for Meteorology, Ionosphere, and Climate mission). The occurrence rate of ionospheric Flayer scintillation was found to be apparently decreased by about 30% during the SSW period. This phenomenon was obviously seen in American sector (90°W–0°) and African sector (0°–90°E). Another prominent feature was the ~0.5 local time hour delay of maximum scintillation occurrence rate associated with the suppression of equatorial Flayer irregularities in the first 2 hr after the sunset during the SSW event in January 2013. It is the first time to study the response of small scale structure in ionosphere during SSW by COSMIC data setsThe occurrence rate of ionospheric F‐layer scintillation weakened by about 30% during the January 2013 SSW eventThe weakening is obvious in American and African sectors, not obvious in other sectors, which are attributed to low scintillation in winter

This study examined the FORMOSAT‐3/COSMIC radio occultation soundings of total electron content in the ionosphere (from 150 to 550 km) and refractivity index in the lower atmosphere (from 0 to 60 km) after/during the 2011 Mw9.0 Tohoku earthquake/tsunami. The refractivity index observations show the first evidence of the Tohoku earthquake/tsunami‐induced vertical oscillations in the lower atmosphere. The atmospheric oscillations with vertical wavelength ranging from 0.5 to 8 km and from 10 to 40 km, respectively, appear in the stratosphere and ionosphere after the earthquake onset. The short vertical wavelengths suggest that the oscillations are the atmospheric oscillatory tail due to the wavefront of the earthquake/tsunami. The radio occultation technique is a tool for detecting the atmospheric waves induced by earthquake or some other sources. It has been well known that the sudden uplift of the Earth's surface due to earthquake/tsunami significantly disturbs the upper atmosphere and ionosphere. However, the evidence of earthquake/tsunami‐induced waves in the lower atmosphere is insufficient due to the lack of observation supporting. Here the FORMOSAT‐3/COSMIC (F3/C) radio occultation refractivity index is for the first time to capture the Tohoku earthquake‐induced vertical oscillations at the stratosphere altitudes from 30 to 40 km. The results in this study not only shed lights on understanding of earthquake/tsunami waves perturbing the whole atmosphere but also suggest that the radio occultation technique can benefit to the earthquake/tsunami warning system. The study shows the first evidence of the Tohoku earthquake/tsunami‐induced vertical oscillations in the stratosphereAtmospheric oscillations with vertical scale range from 10 to 40 km and from 0.5 to 8 km, respectively, in the ionosphere and stratosphereThe oscillations are mainly the atmospheric oscillatory tail due to the tsunami

Wind data observed by a Fabry‐Perot interferometer (FPI) and a meteor radar (MR) deployed in two stations, which are 430 km apart in ground distance, are used to study wind climatology in mesosphere/lower thermosphere over central China and compare between the measurements. A general morphologic similarity of the FPI winds and MR winds is identified with 4 year data since November 2011. At 87 km, the wind vector plots show that the FPI and MR winds agree with each other very well in all months. The zonal winds of both instruments have an apparent semiannual variation with a maximal strength of −20 m/s at around 18:00 UT in equinoctial months, and the meridional winds from both instruments have an apparent annual variation with a maximal strength of −40 m/s at around 15:00 UT in summer months. The correlation coefficients between the measurements of the two instruments are about 0.95 for meridional wind and 0.90 for zonal wind. At 97 km, the wind vector plots show that FPI and MR winds agree with each other from May to October and are obviously different in the rest months. There are very weak semiannual variations at around 18:00 UT for both zonal winds and pronounced annual variation at around 13:00 UT for both meridional winds. The correlation coefficients between the FPI and MR winds are 0.73 for zonal wind and 0.86 for meridional wind, which are overall smaller than that at 87 km. A Gaussian distribution of airglow profile is used to investigate the deviations associated with peak height and full width at half maximum (FWHM) of airglow layer. It is found that the variation of peak height could lead to about 20% variation of correlation coefficients between measurements at the height of 87 km and about 14.8% at the height of 97 km on average. The variation of FWHM could lead to a correlation coefficient variation of about 2.4% and 3.5% at the height of 87 km and 97 km, respectively. Some other reasons, such as the influence of geomagnetic field on meteor trail and the propagation of gravity waves, could also contribute to these differences between measurements. Over 4 year comparison of FPI and meteor radar wind over ChinaCorrelation coefficient of FPI/MR wind stronger for meridional than zonal stronger at 87 km than 97 kmInfluence of airglow variation on FPI wind