The oceanic tidal magnetic field, mainly driven by the circular orbital motion of the Moon, is an essential part of the time-varying geomagnetic field. The previously adopted time-harmonic (TH) base worked well in fitting the primary tidal field, but extracting the other weaker modes like the was difficult with only a single satellite. The tidal field, although it can be derived fortuitously by the gradient data set relying on the side-by-side measurements of Swarm, remains a significant challenge in single satellite measurement. Here, we introduce the ephemerides predictor (EP) base, which corrects the Moon's eccentric orbit, to study the tidal fields based on the pre-processed data set of China Seismo-Electromagnetic Satellite (CSES) and Swarm-Alpha. Our results suggest that the EP base is able to derive the tidal fields of both and when the gradient data set is unavailable.

Because heavy-ion abundance ratios and charge states are largely stable within several solar radii of the Sun, they are widely used to diagnose solar wind source regions and the underlying energy-release processes. However, the relationship between these heavy-ion properties and the magnetic field types of their corresponding source regions remains not fully understood. In this work, we construct a data set of 74 events spanning 1998-2017, each providing a complete linkage between the solar source-region magnetic field configuration, coronal mass ejection (CME) properties, and the corresponding in situ interplanetary CME observations. Our analysis demonstrates that the source-region magnetic morphology is a primary parameter governing solar wind heavy-ion charge states, whereas its influence on the heavy-ion abundance ratio is comparatively weaker. For a given magnetic field type, heavy-ion abundances and ionization levels increase exponentially with the strength of associated X-class flares and are further modulated by the longitudinal location of the eruption source region.

Auroral visibility forecasting at mid-latitudes is inherently challenging because these regions lie near the equatorward boundary of the auroral oval, where small boundary shifts can determine visibility. In East Asia, this sensitivity is further amplified by substantial deviations of the geomagnetic field from dipole approximations. We developed OVATION-AACGM by integrating the Altitude-Adjusted Corrected Geomagnetic (AACGM) v2 coordinate system into the publicly available OVATION Prime 2010 and evaluated its performance for forecasting at Mohe, China (53.5 degrees N, 122.3 degrees E; AACGM latitude similar to 48.7 degrees N). Using over 2 years of matched Defense Meteorological Satellite Program (DMSP)/Special Sensor Ultraviolet Spectrographic Imager observations and OVATION outputs, we derived optimal visibility thresholds for both coordinate systems. The AACGM system yields an optimal threshold of 1,040 km, corresponding to a physically realistic auroral elevation angle of similar to 6.0 degrees. In contrast, the dipole threshold by maximizing the F1 score (1,730 km) corresponds to -1.3 degrees, effectively placing the aurora below the geometric horizon. AACGM-derived distances show improved agreement with DMSP observations (correlation 0.771 vs. 0.709; mean bias -154.5 km vs. +537.9 km). Independent validation of the OVATION-AACGM model performance using 140 nights of ground-based optical observations demonstrated operational skill, achieving 72.7% precision and 80.0% recall. A logistic regression model further provides a continuous probability-distance relationship for auroral visibility. These results demonstrate that coordinate system selection fundamentally influences the physical interpretability of mid-latitude aurora visibility thresholds and support the adoption of AACGM v2 for physically consistent and operationally reliable applications in the Asian sector.

Heavy ions upstream and downstream of interplanetary shocks are not only subject to acceleration, heating, and spatiotemporal modulation during their propagation in interplanetary space, but they can also, in turn, influence the dynamical properties of the shocks themselves. Using ACE/Solar Wind Ion Composition Spectrometer observations, we analyzed the heavy-ion characteristics associated with 163 interplanetary shocks and classified the shocks into four categories for separate examination. We find that most forward shocks are driven by ICMEs, and their occurrence exhibits an 11 yr modulation consistent with the solar cycle, whereas reverse shocks show no clear periodic behavior. Overall, both heavy-ion abundance ratios and average charge states are systematically higher in forward shocks than in reverse shocks. For forward shocks, weak and strong shocks exhibit broadly similar trends: the heavy-ion parameters remain relatively steady prior to shock arrival, followed by a pronounced enhancement immediately after the shock crossing. Events with larger Alfv & eacute;n Mach numbers tend to show steeper and stronger increases. In contrast, both the heavy-ion abundance ratios and average charge states decrease to their minimum values before the arrival of reverse shocks and gradually recover afterward. This behavior suggests that reverse shocks reorganize the spatial distribution of heavy ions as they propagate through interplanetary space.

Abstract The plasmapause boundary can efficiently modulate magnetosphere-ionosphere coupling. During typical geomagnetic storms, the eroded plasmapause displays periodic oscillations that manifest as giant undulations of the aurora in the ionosphere. However, it remains unresolved whether such plasmapause oscillations occur during extreme storms. Here, we confirmed the occurrence of periodic plasmapause oscillations during the most intense superstorm over the past 20 years. Based on the auroral giant undulations, the extremely eroded plasmapause, down to 2 Earth radii (R E ), oscillated periodically at a scale of 1 R E in response to the May 2024 superstorm. Furthermore, we analyzed different and similar signatures of plasmapause oscillations during this superstorm and compared them with the signatures during typical storms. Our results suggest that plasmapause oscillations are an intrinsic and systematic pattern of external explosive energy input into the inner magnetosphere, thus providing physical constraints for global coupling models when addressing the extreme space weather conditions.

Charge exchange between solar wind protons and local hydrogen atoms generates hydrogen energetic neutral atoms (H-ENAs) in the extended neutral hydrogen corona surrounding Mars. The following collisions between H-ENAs and atmospheric molecules generate a distinct proton aurora. How the solar wind influences the proton aurora activity in the short term is not well unknown. We found that there are synchronized proton aurora brightening and atmospheric ion loss intensifying on Mars, both controlled by solar wind dynamic pressure, using observations by the Mars Atmosphere and Volatile Evolution spacecraft. Significant erosion of the Martian ionosphere during periods of high dynamic pressure indicates at least five-to-tenfold increase in atmospheric ion loss. An empirical relationship between ion escape rate and auroral emission enhancement is established, providing a new proxy of Mars’ atmospheric ion loss with optical imaging that may be used remotely and with greater flexibility.

Pressure and density are fundamental atmospheric parameters that reflect the mass and thermodynamic structure of the planetary atmosphere. They have a complex spatial distribution and dramatic seasonal variations in the cold, CO 2 ‐dominated Martian atmosphere. However, their seasonal variations on global scales and their quantitative correlations with atmospheric mass, thermal structure and dust activity have not been systematically analyzed. This study uses remotely sensed data from the Mars Climate Sounder to investigate the spatial and temporal variations of the complex Martian atmospheric pressure and density in a global view from the surface to the mesosphere. In the vertical direction, changes in atmospheric pressure and density above 40 km are largely influenced by expansion or contraction effects of the Martian atmosphere in response to annual changes in solar radiation intensity and dust loading, while the atmosphere in the lower 20 km is more sensitive to semiannual variations in total atmospheric mass related to the evolution of the polar ice caps. To quantify the influence of large dust storms on the thermal structure and mesospheric density structure, we applied correlation analysis and found the best correlations for 90‐km density, 35‐km temperature and 23‐km dust. Finally, the quantitative linear relationships between the three are established, which can provide simplified and readily applicable empirical relationship constraints for future modeling studies of the lower thermosphere below 200 km. This is important for future analyses of the upper atmospheric response to dust storms, and also useful for improving the aerobraking design of future Mars exploration missions.

The Ultraviolet Imager (UVI) is one of the four instruments onboard the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) satellite, a collaborative science mission between the Chinese Academy of Sciences (CAS) and the European Space Agency (ESA). The UVI will capture the terrestrial auroral images that depict the energy depositions in the solar wind-magnetosphere coupling system. The primary function of UVI is to image the entire auroral oval at characteristic wavelengths while effectively mitigating contamination from dayglow, achieving a spatial resolution of approximately 100 km or better. The co-axis four-mirror all-reflective optical system provides a circular field of view of 9.97°, enabling coverage of the entire polar region when the spacecraft’s geocentric distance exceeds 50,000 km. This capability allows UVI to continuously monitor the complete auroral oval for over 40 hours. UVI operates in the long wavelength range of the N2 Lyman-Birge-Hopfield (LBH) band, specifically between 160–180 nm. To achieve the required spectral response and significantly reject out-of-band stray light, multilayer coatings are applied to its mirrors. The detector utilized is an intensified charge-coupled device (ICCD), with photons emitted from the phosphor being coupled through a relay lens to the ICCD. By default, the CCD captures one frame (512 × 512 pixels) every two seconds; thus, thirty frames per minute are coadded to produce a single UVI image. This processing can be performed in orbit or on ground to compensate the possible satellite jitters. The detailed geometric and photometric calibration procedures for UVI are elaborated upon in the paper.

The aurorae on Mars are divided into diffuse aurora, discrete aurora and proton aurora. Proton aurora is the most common type of aurora on Mars. The proton aurora on Mars is formed when protons in the solar wind pass through the Martian hydrogen corona and undergo charge exchange to form energetic neutral atoms, which deposit energy in the Martian atmosphere. Previous research results showed that the main external factors that affect the occurrence rate, emission enhancement, intensity and peak height of proton aurora are the solar wind particle flux and velocity, solar zenith angle and solar longitude. Here, we extend the previous proton aurora database compiled by Hughes et al. [2019], which was in the descending phase of the last solar cycle between 2014-2018, to present with similar algorithm. Using this new database covering almost one solar cycle, we investigated the long-term variations of the proton aurora on Mars in three timescales, including the solar rotation cycle, Martian season, and solar cycle. The results will help us understand the solar wind-Mars interactions.

Auroras on Earth are closely linked to solar activity, offering a valuable way to investigate variations in solar activity, particularly for periods when solar activity data are scarce. This study compares and analyzes auroral records from Korea and mid-latitude Europe between 1610 and 1810 AD. Both Korean and European aurora records show consistency between auroral activity and solar variations, with distinct advantages in different periods. Before 1700 AD, Korean auroral observations were more frequent than European auroras and aligned well with solar activity proxies, making them particularly useful for studying solar variability during the Maunder Minimum. After 1700 AD, European auroral records became more abundant than Korean auroral records and consistent with solar activity, providing better insights into post-Maunder Minimum solar variations and long-term solar activity trends. Thus, Korean and European auroral data complement each other, enhancing our understanding of historical solar activity.

The dual-wavelength extreme ultraviolet camera (EUC) for the Queqiao-2 relay satellite of the Chang’E-7 (CE-7) mission operates at 30.4 and 83.4 nm independently to simultaneously image the plasmasphere, magnetosheath, and ionospheric outflow from a lunar orbit. Each channel of the EUC is consisted of a concave multilayer mirror and a photon-counting imaging detector. This simple system achieves a large field of view (FOV), high spatial resolution, and optimized photon transmission efficiency to capture high-quality images of very weak extreme ultraviolet emissions in Earth space. Here we present the detailed design, tests, and calibrations of the EUC. Ground geometrical tests showed that the FOV was 20.2° for the 30.4 nm channel and 20.3° for the 83.4 nm channel, and the spatial resolution was 0.09° for both channels. Geometric distortion was corrected to be less than 1

Many planets, including the Earth, possess a global dipolar magnetic field. To diagnose the interior source of the dipolar field, researchers usually adopt a dipole model consisting of six parameters to fit the observed dataset of the magnetic field. However, the simultaneous fitting of these parameters often leads to multiple local optimal parameter sets. To address this fitting dilemma, Rong ZJ et al. (2021) recently developed a current loop model. This technique can successively separate and invert the loop parameters. Here, we further show how this technique can be reduced and modified to fit a dipole model. Applications of this reduced technique to the International Geomagnetic Reference Field model and the Martian crustal field model highlight its unique ability to diagnose both the planetary global dipolar field and the local crustal field anomaly, a capability that sets it apart from existing methods. The potential impact of this technique on geomagnetism and planetary magnetism is significant, given its unique ability to diagnose both the planetary global dipolar field and the local crustal field anomaly.

This study presents a comprehensive analysis of key meteorological parameters at the Lenghu site, a premier astronomical observing location, with particular emphasis on understanding their variability patterns and long-term trends. The research systematically investigates regional distribution characteristics, periodic variations, seasonal changes, and the temporal evolution of critical atmospheric parameters that influence astronomical observations. Furthermore, this study explores the potential connections between these parameters and major climate oscillation patterns, including ENSO (El Niño–Southern Oscillation), PDO (Pacific Decadal Oscillation), and AMO (Atlantic Multidecadal Oscillation). Utilizing ERA5 (the fifth-generation atmospheric reanalysis from the European Centre for Medium-Range Weather Forecasts) reanalysis data, we examine the regional atmospheric conditions (82°–102° E and 31°–46° N) surrounding the Lenghu site from 2000 to 2023 (24 years). The analysis focuses on fundamental meteorological parameters: precipitable water vapor (PWV), temperature, wind speed at 200 hPa (W200), and total cloud cover (TCC). For the Lenghu site specifically, we extend the temporal coverage to 1990–2023 (34 years) to include additional parameters such as high cloud cover (HCC) and total column ozone (TCO). The analysis reveals that the ENSO and PDO indices are negatively correlated with W200. The AMO index has a positive correlation with PWV and a slight positive correlation with W200, temperature, and TCO. Moreover, a comparative analysis of Lenghu, Mauna Kea, and Paranal reveals distinct variation trends across sites due to regional climate differences. Notably, while all observatory sites are affected by global climate change, their response patterns and temporal characteristics exhibit subtle variations.

Plasmapause surface waves (PSWs) and plasmaspheric plumes are two crucial phenomena of magnetosphere-ionosphere coupling system in response to geomagnetic disturbances. However, it remains elusive what the potential interaction exists between them. In this letter, we identify the penetration of PSWs into the plasmaspheric plume and their interaction with each other. After the PSWs penetrating into the plume structure, they can oscillate the plume and cause the periodical scattering and precipitation of thermal particles. Meanwhile, the foundational frequency of PSWs in the plume becomes lower, and the higher-harmonic frequencies of PSWs are simultaneously observed. Their corresponding energy of modulated and precipitating particles also reduces to <210 eV, which is different from the <1 keV electrons and <50 keV ions in those ordinary PSWs occurring near the main plasmapause. Our results advance our understanding of the complex interplay effect among various dynamic structures in the dusk inner-magnetosphere and aurora region.

Dust activity on Mars is not physically different in nature from that on Earth, except that it is more intense and critical to the Martian climate under the specific planetary and atmospheric parameters of Mars. Previously found atmospheric dust tides during large Martian dust storms are a significant short-term global-scale dust activity, analogous to Earth's ocean tides. However, it is not certain whether dust tides are widespread on Mars. In this paper, we use multi-local time observations of Martian year (MY) 33 from the Mars Climate Sounder to provide the first detailed overview of dust tides over the entire MY. We generalize two scenarios of dust tides from the spatial distribution of the day-night difference of dust, called the low-latitude scenario and the low-altitude scenario, respectively. The two scenarios are ubiquitous and show distinct seasonal variations. For the first time, we find a downward phase progression signal in the atmospheric dust abundance, similar to the vertical propagation of thermal tides, providing direct evidence for the role of vertically propagated thermal tides in driving the diurnal variations of dust. Utilizing the Lagrangian particle simulation, we show that the diurnal dust motion in both scenarios is driven by meridional and vertical tidal winds. This implies that the associated wind fields can be inferred inversely from the diurnal variations of the airborne dust and can be used to indirectly estimate global wind fields. The relatively simple Martian atmosphere could also be used to test and advance existing theories of Earth's dust activity.

Previous studies suggested that Mercury's magnetosphere could possess Earth-like field-aligned currents (FACs) despite the absence of an ionosphere. However, due to the limited coverage of spacecraft observations, our understanding of Mercury's FACs is scarce. Here, we employed Amitis, a hybrid-kinetic plasma model, to investigate the establishment and global pattern of Mercury's FACs. The responses of Mercury's FACs to various interior conductivity profiles and different orientations of the upstream interplanetary magnetic field (IMF) were simulated. It has been shown that the profile of a less resistive upper layer and a conducting core favors the establishment of FACs. Three types of large-scale FACs (Region 1-like, Region 2-like and NBZ-like FACs) are shown in simulations. Comparison with previous observations suggests that Mercury's effective conductance for closing R1-like FACs is similar to 2.4-3.4 S. The influence of IMF orientation on FACs is similar to that observed in Earth's magnetosphere, but the response of the R2-like FACs to the IMF orientation is different.

Abstract Plasmapause surface waves (PSWs) near the plasmapause boundary are regarded to be the magnetospheric source of ionospheric auroral giant undulations (GUs) located at the equatorward boundary of diffuse aurora. However, the observational evidence of wave‐particle interaction connecting PSWs and GUs is absent. In this letter, we demonstrate GUs are driven by pitch‐angle scattering of time domain structures modulated by the PSWs, based on the conjugated ionospheric and magnetospheric observations. Specifically, ionospheric GUs are lighted by the pitch‐angle scattering of <1 keV thermal electron and ions and energetic ions with energy up to dozens of keV near the plasmapause. Further, the total fluxes during one PSW period and energy of scattered electron and ions determine the size and luminosity of GUs. Our research provides observational evidence that PSWs cause periodic electron precipitation via modulating the time domain structures rather than the previously predicted chorus or electron cyclotron harmonic waves.

This paper statistically analyzes the seeing data at the Lenghu site Platform C from 2018 to 2024, during which extensive construction modified the original landscape. The study focuses on the impacts of meteorological factors and building obstructions. The results reveal a progressive degradation in seeing as the monitoring setup passively changed: the median values were 0.'' 76 (the original location), 0.'' 83 during the Terrace, and 0 .'' 99 at the new Dome (temporarily considered the permanent monitoring location). Once the instruments are fully deployed, wind speed and wind direction critically affect seeing quality, with optimal conditions occurring when the wind speed is 2-6 m s(-1) and the wind direction is between 180 degrees and 270 degrees. However, in 2023 and 2024, the wind speeds decreased, and the prevailing wind direction shifted from southwest to northwest, correlating with poorer seeing. Computational Fluid Dynamics simulations reveal that the construction of the Wide Field Survey Telescope altered the local wind field, increasing turbulence around the Dome, especially when the winds blow from 225 degrees to 255 degrees. In contrast, Platform A, located in a higher and more open area, consistently maintained better seeing, particularly after midnight, likely due to fewer obstructions and lower nocturnal heat release.