In this study,we present an innovative Mars Ionosphere-Thermosphere Model(MITM),which is a time-dependent,three-dimensional(3-D)model that comprehensively represents the self-consistently coupled thermosphere and ionosphere of Mars within the altitude range of 70-300 km.The model incorporates an extensive range of parameters,including neutral number densities of CO2,CO,O,O2,N2,NO,N(2D),N(4S),Ar,and He;ion number densities of CO2+,CO+,O+,O2+,N2+,NO+,N+ions,and electrons;neutral temperature;and neutral wind fields.The MITM code employs a high-resolution grid system in a spherical geographical coordinate system,with a horizontal resolution of 5° latitude by 7.5° longitude.This altitude-resolved grid system enables accurate depiction of spatial variations in the Martian thermosphere and ionosphere.To showcase the capabilities of the MITM,we present two simulation cases:one during the equinox and another during the solstice.Both simulations reproduce key features of the Martian thermosphere and ionosphere including the characteristics of horizontal circulation,diurnal variations in chemical composition,and distribution of electron density.The MITM offers a robust framework for understanding the intricate interactions and processes that shape the Mars thermosphere and ionosphere,which are crucial for enhancing our understanding of Martian upper atmosphere and ionosphere.

Sanya (18.3°N, 109.6°E) Incoherent Scatter Radar (SYISR) is a newly built ISR in low latitude China. The unique features of SYISR include a single-channel directly connected T/R unit and antenna, a radar array monitoring and calibration network, environmental adaptability design and open architecture. Since 2022, we have run SYISR almost continuously. In this presentation, at first we will generally describe the technical details of SYISR. Then we will show the ionospheric observations made by SYISR, including equatorial bubble, ion line and plasma line results, and derivation of low latitude neutral wind and ionospheric electric field. At the end, we will introduce the development status of the SYISR Tristatic System.

Led by the Institute of Geology and Geophysics, Chinese Academy of Sciences, we have built a brand‐new modular active digital phased array, with all solid‐state transmission and digital receiving incoherent scatter radar (ISR) in Sanya (18.3°N, 109.6°E), a station in low latitude China called Sanya ISR (SYISR) since 2015. The development of SYISR involved the indoor design and development of key components, an outdoor prototype test, and the production and debugging of the entire array. The unique features of SYISR include a single‐channel directly connected T/R unit and antenna, a radar array monitoring and calibration network, environmental adaptability design and open architecture. The entire radar has 4,096 channels and 5,930 modules in total. All the technical indices, mainly including a >2 MW peak power, a 43 dBi antenna gain and a <120 K noise temperature, either meet or are superior to the designed value through an independent evaluation. Waveforms of single pulse, linear frequency modulation, Barker code, long pulse and alternating code have been implemented to meet multiple purposes. Four observational modes for ionospheric experiments, including zenith stare, perpendicular to geomagnetic field, meridian scan, and all sky scan, have been developed. We have implemented time domain decoding, frequency domain decoding, and statistical inversion methods in calculating the autocorrelation function and power spectra in signal processing. The preliminary experimental results on ionospheric parameters, plasma lines, irregularities and hard targets are reasonable and encouraging, which greatly enhances our confidence in achieving our scientific goals in the future.

China’s Mars rover, Zhurong, touched down on Utopia Planitia in the northern lowlands of Mars (109.925° E, 25.066° N) in May 2021, and has been conducting in situ investigations of the landing area in conjunction with the Tianwen-1 orbiter. Here we present surface properties derived from the Zhurong rover’s traverse during the first 60 sols of rover operations. Our analysis of the rover’s position from locomotion data and camera imagery over that time shows that the rover traversed 450.9 m southwards over a flat surface with mild wheel slippage. Soil parameters determined by terramechanics, which observes wheel–terrain interactions, indicate that the topsoil has high bearing strength and cohesion. The soil’s equivalent stiffness is estimated to range from 1,390 to 5,872 kPa per mN, and the internal friction angle ranges from 21° to 34° under a cohesion of 1.5 to 6 kPa. Aeolian bedforms in the area are primarily transverse aeolian ridges, indicating northeastern local wind directions. Surface rocks imaged by the rover cameras show evidence of physical weathering processes, such as wind erosion, and potential chemical weathering processes. Joint investigations utilizing the scientific payloads of the rover and the orbiter can provide insights into local aeolian and aqueous history, and the habitability evolution of the northern lowlands on Mars. Analysis of interactions between the wheels of the Zhurong rover and the terrain along the rover’s traverse reveals soils with high bearing strength and cohesion.

An incoherent scatter radar in southern China will probe low-latitude ionospheric properties while also sensing meteors and space debris, explain the SYISR leadership team.

Using the electron density profiles from Mars Global Surveyor Radio Occultation observations, the ionospheric longitudinal wave-3 (WN3) structure with different frequencies is investigated. The semidiurnal component is the dominant component for the entire Mars ionosphere profile at northern high latitudes. Both diurnal and semidiurnal components manifest double peaks in altitudinal variations in amplitude, which are 5-15 km lower than the ionospheric M1 and M2 peaks. The phase generally increases with altitude and shows a rapid rate of increase around the M2 peak. To interpret the altitudinal variation in amplitude and phase, we then derive the tidal coupling equation to elucidate the impact of atmospheric tides on the Mars ionosphere. Under the assumption of photochemical equilibrium, the tidal coupling equation indicates that the log density gradient of electrons (kN ${k}_{N}$) critically modulates the ionospheric response to atmospheric tides. In the observations, a positive correlation between the kN ${k}_{N}$ profile and the amplitude of the WN3 structure at altitude is found. The solar longitude variation in the kN ${k}_{N}$ peaks also agrees with the vertical movement of the amplitude peaks of the WN3 structure along the solar longitude. The rapid phase increase corresponds to the abrupt decrease in kN ${k}_{N}$ around the M2 peak. These observational results agree with the tidal coupling equation prediction, thereby supporting that the interpretation of kN ${k}_{N}$ in modulating the altitudinal variation in the WN3 structure is reasonable.

Global Navigation Satellite System (GNSS) radio occultation (RO) has been an active method to explore the earth’s atmosphere since 1995. RO-inverted bending angles have significantly contributed to atmospheric weather and climate research via data assimilation. However, the used bending angles still contain residual ionospheric error (RIE) after the well-known linear combination correction and should be removed. In this study, we propose to calibrate the RIE using ray-tracing RO bending angle profiles for the first time. The ionospheric background used for ray-tracing was obtained by a Kalman filter data assimilation algorithm through ingesting multisource ionospheric data. More than 380,000 COSMIC RO events during 2008–2013 were simulated via the EGOPS software for statistical calibration. To evaluate the improving performance, we focus on analyzing the deviation of the bending angle from that of National Center for Atmospheric Research climatology results between 60 and 80 km before and after the calibration. It is found that the amplitude of RIE during daytime is significantly reduced. The ‘three troughs’ feature of RIE due to the ionosphere is almost eliminated. The solar activity dependence of RIE can also be calibrated to some extent. We further define a parameter named calibration efficiency to evaluate the calibration performance of the method is > 40% at low latitudes and > 80% at the ‘three troughs’ regions. The results demonstrate that our calibration method works well. It could be potentially used to reduce the RIE in GNSS RO bending angles.

A new incoherent scatter radar (ISR) has recently been dedicated at Sanya (SYISR), China (geographic 18.34°N and 109.62°E) to detect the low‐latitude ionospheric plasma by conducting continuous operation and electronic beam steering on a pulse‐to‐pulse basis. This paper provides an overview of the processing procedure of SYISR ion line data and presents some preliminary observational results under various transmitting signal schemes and different working modes, such as the zenith‐directed mode and meridional and zonal scanning modes, with comparison to the international reference ionosphere model (IRI‐2016), ionosonde and Ionospheric Connections Explorer (ICON) satellite measurements. The diurnal and altitude versus latitude variation characteristics of electron density ( N e ), electron temperature ( T e ), and ion temperature ( T i ) are in accordance with those of other ISR measurements in mid‐low latitudes, and IRI shows some discrepancies with SYISR observations, including the sunrise and sunset enhancement in SYISR_ T i and the overestimated IRI_ T e . The comparison between the daytime SYISR_ T i and ICON_ T i shows good consistency based on 31 observational samples. The measurement of line‐of‐sight velocity ( V i ) for long pulse can reveal the properties of the medium scale traveling ionospheric disturbances manifesting the radar's potential to study the mesoscale ionospheric variation in the Sanya area. The derived vector velocities with a better measurement accuracy during the day are generally in line with ionospheric plasma physics. The results show that SYISR can obtain continuous ionospheric parameters through multi‐beam scanning measurements at ∼700 km horizontal scale, which provides important information for studying the atmosphere‐ionosphere‐magnetosphere coupling and ionospheric scintillation at low latitudes in East Asia.

Low‐frequency waves are closely related to magnetospheric energy dissipation processes. The Cassini spacecraft explored Saturn's magnetosphere for over 13 years, until September 2017, covering a period of more than a complete solar cycle. Using this rich heritage data set, we systematically investigated key physical parameters of low‐frequency waves in Saturn's magnetosphere, including their local time distribution and the dependence on solar activity. We found that the wave activity peaked in the near noon sector. For the nightside, the wave intensity also appeared to peak pre and postmidnight. Due to the limited local time coverage for each solar phase, we were not able to draw a firm conclusion on the wave's dependence on solar activity. In general, the wave power showed a monotonically decreasing trend toward larger distances in nightside sectors especially during the declining phase, which implied that low‐frequency waves mainly originate from the relatively inner regions of the magnetosphere. On the dayside, stronger waves were mostly located at/within ∼25 Rs, near the magnetopause. The study shows a global picture of low‐frequency waves in Saturn's magnetosphere, providing important implications for how magnetospheric energy dissipates into Saturn's polar ionosphere and atmosphere.

Using GCITEM-IGGCAS model, we simulate the influence of the eastward propagating non-migrating diurnal tide with zonal wavenumber-3 (DE3) on nitric oxide (NO) infrared cooling rate. We find that the DE3 tide can drive a DE3 signal in lower thermospheric NO cooling rate, and the simulated altitudinal and seasonal variations are according with that of DE3 signal in equatorial lower thermospheric NO cooling rate observed by Oberheide et al. [2013], which is based on the TIMED/SABER observations during the solar minimum year 2008. This signal mainly shows an annual variation, which is stronger between June and September, and weaker near November. The maximum of the absolute signal, whose value is about 0.35*10-9 W/m3, occurs near the height of 130 km, but the relative signal mainly shows its peak with a value of 40% near the height of 100 km. Due to the difference of the driving mechanism, the distribution of NO signals in different latitudinal regions shows obvious difference. The middle- and low-latitude NO signal show smooth variation, while the high-latitude signal is discontinuous. The DE3 signal in NO cooling rate is mainly controlled by DE3 temperature tide and DE3 NO tide, meanwhile, the influences of DE3 neutral density tide on the DE3 signal can be ignored. The relative contributions of the DE3 NO tide and of the DE3 temperature tide vary with geographic latitude. The DE3 cooling rates in middle- and low- latitude and in high-latitude are respectively mainly driven by the DE3 temperature tide DE3 NO tide. DE3 tide may not only drive the DE3 signal, but also affect the lower thermospheric zonal mean NO cooling rate. The maximum of the absolute influence, whose value is about 0.12*10-9 W/m3, occurs above the height of 140 km, but the relative influence mainly shows its peak with a value of 10% near the height of 100 km.

The Earth’s magnetosphere is the outermost layer of the geospace system deflecting energetic charged particles from the Sun and solar wind. The solar wind has major impacts on the Earth’s magnetosphere, but it is unclear whether the same holds for solar flares—a sudden eruption of electromagnetic radiation on the Sun. Here we use a recently developed whole geospace model combined with observational data from the 6 September 2017 X9.3 solar flare event to reveal solar flare effects on magnetospheric dynamics and on the electrodynamic coupling between the magnetosphere and its adjacent ionosphere, the ionized part of Earth’s upper atmosphere. We observe a rapid and large increase in flare-induced photoionization of the polar ionospheric E-region at altitudes between 90 km and 150 km. This reduces the efficiency of mechanical energy conversion in the dayside solar wind–magnetosphere interaction, resulting in less Joule heating of the Earth’s upper atmosphere, a reconfiguration of magnetosphere convection, as well as changes in dayside and nightside auroral precipitation. This work thus demonstrates that solar flare effects extend throughout the geospace via electrodynamic coupling, and are not limited—as previously believed—to the atmospheric region where radiation energy is absorbed 1 .

Serpentine and carbonate are products of serpentinization and carbonation processes on Earth, Mars, and other celestial bodies. Their presence implies that localized habitable environments may have existed on ancient Mars. Factor Analysis and Target Transformation (FATT) techniques have been applied to hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to identify possible serpentine and Mg-carbonate-bearing outcrops. FATT techniques are capable of suggesting the presence of individual spectral signals in complex spectral mixtures. Applications of FATT techniques to CRISM data thus far only evaluate whether an entire analyzed image (approximate to 3 x 10(5) pixels) may contain spectral information consistent with a specific mineral of interest. The spatial distribution of spectral signal from the possible mineral is not determined, making it difficult to validate a reported detection and also to understand the geologic context of any purported detections. We developed a method called Dynamic Aperture Factor Analysis/Target Transformation (DAFA/TT) to highlight the locations in a CRISM observation (or any similar laboratory or remotely acquired data set) most likely to contain spectra of specific minerals of interest. DAFA/TT determines the locations of possible target mineral spectral signals within hyperspectral images by performing FATT in small moving windows with different geometries, and only accepting pixels with positive detections in all cluster geometries as possible detections. DAFA/TT was applied to a hyperspectral image of a serpentinite from Oman for validation testing in a simplified laboratory setting. The mineral distribution determined by DAFA/TT application to the laboratory hyperspectral image was consistent with Raman analysis of the serpentinite sample. DAFA/TT also successfully mapped the spatial distribution of Mg-serpentine and Mg-carbonate previously detected in CRISM data using band parameter mapping and extraction of ratioed spectra. We applied DAFA/TT to CRISM images in some olivine-rich regions of Mars to characterize the spatial distribution of Mg-serpentine and Mg-carbonate-bearing outcrops.

The solar wind interaction of small‐scale lunar magnetic anomalies remains unsolved due to lack of in situ observations. A dedicated coordinate system is established here to reconstruct the distributions of two remotely sensed symptoms of this interaction: the low‐frequency whistlers and reflected protons. It is found that these whistlers form a pair of wings beside the Moon and they originate from the low‐altitude interaction region, instead of from the higher altitudes where the reflected protons arrive and the associated shocks possibly form. Electrons and protons may behave differently in the interaction region. The incident electrons remain in a fluid state and may be diverted by the anomalies, exciting the low‐frequency whistlers. The protons, however, become unmagnetized and are reflected specularly by the vertical electric fields. These electric fields may derive from the charge separation/different motions of the electrons and protons, although the presence of low‐altitude shocks cannot be ruled out completely.

Incoherent scatter radars (ISR) are among the most powerful ground‐based instruments for solar‐terrestrial physics, measuring multiple plasma parameters over almost the entire vertical extent of the ionosphere. In Sanya, on Hainan Island, China, an advanced high‐power phased array ISR, known as the Sanya incoherent scatter radar (SYISR), is under construction. A tristatic system is planned, with a transmitter at Sanya (SY) Station (109.6°E, 18.3°N), together with receivers at SY, Fuke (FK) (109.1°E, 19.5°N), and Qiongshan (QS) (110.2°E, 19.7°N) on Hainan Island. With the pulse width increasing, the SNR increases for a phased array monostatic ISR, while the SNR initially increases and then remains unchanged for a phased array bistatic ISR. SNR first increases and then decreases as the detection height increases from 100 km to 1,000 km for both the monostatic and bistatic ISR for typical ionospheric conditions. The relative error decreases fast with increasing pulse width when the pulse width is lower than 130 μs for both monostatic and bistatic ISR. When the pulse width is over 130 μs, the relative error decreases very slowly for a monostatic ISR, while it decreases very slowly and then stays unchanged with increasing pulse width for a bistatic ISR. Relative error increases slowly below 500 km, but increases fast for heights over 500 km for both the monostatic ISR and bistatic ISR. It is shown that a tilt angle of 20°–30° and a clockwise‐rotation angle of 157° are reasonable choices for the FK receiving array in the SYISR tristatic system.

The theoretical spectrum of incoherent scattering is the theoretical basis for understanding the detection of incoherent scatter radar. The solution process can be summarized into the microscopic method based on the work of Hagfors (1961) and the macroscopic method based on the framework of Farley (1960). In this paper, the above two methods are used to solve the theoretical spectrum of collisional non-magnetized plasmas, separately. The normalized admittance and polarizability of plasma and the differential scattering cross section and spectral density function of incoherent scattering are analyzed, and the mathematical relationships between them are obtained. A general analysis of the similarities and differences between the two methods in the theoretical choice, the final conclusion and a variety of factors are given.

Mars is not only our nearby but also the most Earth-like planetary neighbor. Scientific exploration of Mars is thus of crucial value to our understanding of the solar system. The existence of abundant evidence for the former presence of water on Mars demands further exploration for signs of life on our sister planet, and investigations that could shed light on conditions favorable to the origin of life.

With Magnetospheric Multiscale Mission (MMS) observation of a magnetic flux rope of ion scale in magnetopause, we apply the single-point method presented by Rong et al., [2013] to study the magnetic field structure of flux rope. The calculated geometric parameters, e.g. axis orientation, helical handedness, current density, curvature radius, and boundaries of flux rope show well consistency with those derived from the multi-point methods. Thus, the single-point method of Rong et al., [2013] is reliable for studying the interior field structure of magnetic flux rope and could be applied widely to single-point spacecraft missions that examine the dynamics of flux rope.

Using GCITEM-IGGCAS model, this study investigates ionosphere' s responses to DE2's Hough modes from below by both electro-dynamical coupling and the upward tidal wave propagation. We put different Hough modes in the model as lower boundary to simulate electron density's variation of ionosphere, and then separate the responses of two mechanisms in details. The results show that the ionosphere due to DE2' s four Hough modes all show semi-annual variation, with the peak appearing at spring and autumn, and the trough at winter and summer. The response of equator symmetric mode appears four peaks and troughs in one day, and other three modes' responses show only one peak and trough. The equator symmetric mode is the most important one of four Hough modes, and its effect shows a wave pattern, with main wave number of WN3 dominated by electro-dynamical coupling. The other modes weaken the variation of ionosphere's electron density. This method helps us to understand how the non-migrating tide affecting ionosphere.

Transpolar arcs that occur primarily under northward interplanetary magnetic field (IMF) are a class of auroral features in the polar cap region. Many mechanisms have been proposed to interpret the generation of the arcs, including reconnection and sudden change in the IMF. It is now generally accepted that IMF BYcomponent plays a key role in the generation and evolution of the arcs. Here we report an interesting long-lasting and moving transpolar arc observed during a geomagnetically quiet period (Dst<10 nT and AE<50 nT) by the wide-field auroral imager (WAI) onboard the Chinese Fengyun satellite. The WAI is a recently launched imager operated in far ultraviolet wavelength (LBH band in 140-180 nm) in a sun-synchronous orbit with a height of ~840 km. It is shown that the arc was initiated at the poleward auroral boundary on dawnside after the IMF turned to be northward and persisted for more than 5 hours. The arc moved toward the noon-midnight line as the IMF BYcomponent changed its direction and then moved back toward dawnside. An interesting phenomenon was that the arc was accompanied with strong energetic proton (30-80 keV) precipitations with geomagnetic latitude greater than 70° but no significant electron precipitations. However, the origin of these energetic protons is unknown and is worthy study in future.