空间科学学报

Monthly Precipitation Forecast in Shaoyang Region Based on Sunspots

ZHAO Haijuan, SUN Feifei, LIU Dandan, ZHANG Qiang, GUO Jianguang, XIE Jinping, LI Jianzhu

, Available online , doi: 10.11728/cjss2026.05.2025-0220

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Abstract:
The prediction of monthly precipitation is of great significance for water resource utilization and water conservancy project scheduling. The core work of this study includes: proposing a new sunspot R_SSNy index and constructing an RBF forecasting model; construct a Multilayer-Perceptron (MLP) monthly precipitation forecast model based on the R_SSNy index prediction value; construct the Rainfall Abundance Index (RAI) to overcome the contradiction between local and global optima, and using MLP for RAI prediction. The results show that: the Radial Basis Function network (RBF) forecasting model of R_SSNy index performs well in the calibration, validation, and prediction stages, with a relative error of less than 10% for 93% of the predicted values in month t+1; the training and testing sets of the MLP monthly precipitation forecast model have good performance, with R² values of 0.99 for both sets; the defined RAI index provides an effective tool for the quantitative assessment of precipitation abundance and scarcity states, and holds value for further research deepening and application promotion; the MLP monthly RAI forecast model performs well and meets the accuracy requirements. The research on monthly precipitation forecast based on sunspots has pioneering significance.

Simulation and Experimental Validation of a Combined Ion Line and Plasma Line Inversion Method for Incoherent Scatter Radar

ZHANG Wenao, WANG Junyi, CAI Yihui, DING Feng, HÄGGSTRÖM Ingemar, YUE Xin’an

, Available online , doi: 10.11728/cjss2026.05.2026-0006

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Abstract:
In the ionospheric monitoring, one of the key techniques is the Incoherent Scatter Radar (ISR), which usually uses the so called ion line spectra resulted from the ion acoustic wave to derive multiple plasma parameters including electron density, electron and ion temperature, and ion velocity and composition. In addition to the ion line, ISR could also measure the so called plasma line spectra due to the existence of Langmuir wave, the dispersion relation of which is associated with the electron density and temperature. In the conventional ion line inversions, the Temperature-Ion Composition Ambiguity (TICA) and the systematic bias hinder the accuracy of retrieved parameters. To address these issues, here we propose an improved method by incorporating the information of plasma line into the ion line fitting process. We expect that the retrieval accuracy could be enhanced with the independent constraint on electron density and electron temperature obtained from the plasma line. Simulations based on the International Reference Ionosphere demonstrate that the combined ion line-plasma line method significantly reduces deviations in electron density and temperature, and it can improve the impact of the TICA effect to a certain extent. The comparison of the experimental results of Sanya Incoherent Scatter Radar with the ionosonde data on 6 June 2022 shows that this method has a certain effect on improving the electron density. This study establishes the feasibility of combined inversion for ISR data analysis, enabling more accurate and calibration-free ionospheric parameter retrievals in the future.

Distribution Characteristics of Nighttime MSTIDs over China and Their Connections with Mid-latitude Spread-F

LI Ke, ZHANG Donghe, SUN Shuji, YANG Guanglin, YU Shimei, HUANG Weiquan, HAO Yongqiang

, Available online , doi: 10.11728/cjss2026.05.2025-0177

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Abstract:
This study investigates the spatiotemporal characteristics of periodic Total Electron Content (TEC) disturbances associated with Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) over the Chinese sector and examines their statistical relationship with Mid-latitude Spread-F (MSF). MSTIDs and MSF are two common ionospheric phenomena occurring at different spatial and temporal scales in the midlatitude F region, and previous studies have suggested that they may be dynamically connected. To clarify this relationship, we use observations from more than 250 Global Navigation Satellite System (GNSS) stations of the Crustal Movement Observation Network of China (CMONOC), together with ionogram data from four ionosonde stations operated by the China Research Institute of Radiowave Propagation (CRIRP). A statistical analysis is conducted to characterize the occurrence, temporal variability, and spatial distribution of nighttime MSTIDs from 2014 to 2023, with particular attention to summer conditions and their association with spread-F events. The results reveal clear solar-cycle and seasonal dependences of MSTID activity in the Chinese sector. Their occurrence rates are substantially higher during solar minimum years than during solar maximum years, and the disturbances occur most frequently during summer nights. Spatially, two distinct regions of enhanced MSTID occurrence are identified, suggesting the influence of different generation mechanisms. The characteristics presented by the eastern peak are basically consistent with those driven or amplified by the MSTIDs associated with the Perkins instability and its related electrodynamic processes. In contrast, the western peak is closely associated with frequent atmospheric gravity wave activity southeast of the Tibetan Plateau, where complex terrain and active convection may provide strong wave sources. Further analysis shows that MSTIDs and MSF frequently occur on the same night and exhibit a relatively stable temporal sequence, with MSTID activity generally preceding the onset of MSF. This chronological relationship suggests that MSTIDs may create favorable conditions for spread-F development by perturbing plasma density gradients, modifying the bottomside F layer, or enhancing polarization electric fields. Although the statistical results do not by themselves establish direct causality, they provide important observational evidence supporting a possible triggering or preconditioning role of MSTIDs in the generation of MSF. These findings improve our understanding of multiscale coupling processes in the midlatitude ionosphere.

Observational on Ionospheric Disturbances Based on the Low-latitude Long-range Ionospheric Radar

DAI Guofeng, LI Guozhu, ZHANG Donghe, HAO Yongqiang, HU Lianhuan, SUN Wenjie, XIE Haiyong, NING Baiqi, ZHAO Xiukuan, LI Yi, LIU Jianfei

, Available online , doi: 10.11728/cjss2026.05.2025-0207

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Abstract:
In the low-latitude ionosphere, the Equatorial Plasma Bubble (EPB) irregularities and Traveling Ionospheric Disturbances (TIDs) are two important space weather phenomena. These disturbances can affect radio wave propagation, disrupting satellite communications and navigation positioning systems. Due to the limitations of ground-based detection techniques, substantial observational gaps remain regarding ionospheric TIDs and irregularities over low-latitude oceanic regions. This study introduces an over-the-horizon detection method for low-latitude ionospheric disturbances using the Low-lAtitude long Range Ionospheric Radar (LARID) located in Hainan, China. By resolving the elevation angle of arrival based on the phase difference between the radar's main array and interferometer array, LARID can determine the spatial location of ionospheric disturbances. Leveraging its multi-beam observation capability, we have achieved two-dimensional imaging of TID structures and retrieved their wavelengths and propagation directions. The localization results for EPBs show good agreement with S₄ index data from GNSS receivers. Significant differences exist between the observed TIDs and GNSS TEC measurements, which may be partly attributed to the filtering effect of daytime westward wind fields on atmospheric gravity waves. While LARID is currently only capable of observing quasi-east/west propagating TIDs and ionospheric irregularities along the east-west direction, this study finally proposes a method to extend its observational azimuth to full 360° coverage. Ray-tracing experiments demonstrate that this expansion can effectively enhance LARID's detection coverage for background ionospheric disturbances and irregularities.

High-precision In-orbit Calibration Technology for the CSES-01 Geophysical-field-detection Satellite

ZEREN ZHIMA, HUANG Jianping, YANG Yanyan, YAN Rui, LIN Jian, ZHANG Zhenxia, CHU Wei, LIU Dapeng, YANG DeHe, XU Song, LU Hengxin, WANG Jie, HUANG He, HU Yunpeng, TAN Qiao, LI Wenjing, ZHOU Na

, Available online , doi: 10.11728/cjss2026.05.2026-0023

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Abstract:
This study focuses on the data calibration challenges of eight types of payloads in four major categories (electromagnetic field, in-situ plasma, energetic particles, and ionospheric structure) carried by the China Seismo-Electromagnetic Satellite (CSES-01, also known as Zhangheng-1), The in-orbit full-chain calibration system for electromagnetic satellite data has been established. Vertically, this system achieves precise end-to-end validation from “raw signals to physical quantities and then to data products” for each payload. Horizontally, it conducts multidimensional cross-validation among payloads, satellites, and ground-based observations, as well as between models and measurements. Overall, the validated data from CSES-01 have reached an internationally advanced level, with some indicators leading globally. The frequency resolution of electromagnetic fields (0.45 Hz), as well as the flux (0.01 MeV) and pitch angle (5°) resolution of high-energy particles, outperform those of DEMETER and POES; the magnetic field accuracy (better than 1 nT) and plasma relative accuracy (better than 10%) are comparable to those of the Swarm satellites; the instrument bias accuracy of the GNSS occultation receiver is comparable to that of COSMIC. The magnetic field data have become an important data source for international models such as IGRF and CHAOS-8. This on-orbit validation technology system establishes a proprietary technical framework in the field of electromagnetic satellites, and has been successfully applied to the data production of the CSES-01 satellite and has driven engineering improvements for the CSES-02 satellite, significantly enhancing satellite observational performance. The validated data products have been applied to earthquake monitoring and space weather research, laying a key technological foundation for China’s transition from “catching up” to “keeping pace” and even “leading” in related technological domains.

Polar Cap Potential Saturation and Ionospheric Convection Patterns during Superstorms

DU Aimin, LUO Hao, GE Yasong, ZHANG Ying, XU Wenyao

, Available online , doi: 10.11728/cjss2026.05.2025-0223

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Abstract:
Five super intense magnetic storms (with minimum Dst < −200 nT) were examined to investigate the relationship between Polar Cap Potential (PCP) saturation and ionospheric convection patterns. A quantitative method was used to determine whether or not PCP was saturated by applying both linear and nonlinear (exponential) fits for each event. The results showed that PCP saturation occurred for two of five. The two events with saturation had distorted ionospheric convection patterns (D-CONV) with asymmetric vortices, while the other three events without PCP saturation had well-known standard convection (S-CONV) with quasi-symmetric twin vortices. The authors conclude that sporadic midnight sector substorm electric fields may contribute to the asymmetric convection patterns and PCP saturation, in agreement with previous speculations. Further analyses are needed to confirm this hypothesis.

Propagation and Evolution of MSTIDs over the Low-Latitude Region of China during 8 December 2019

LUO Ji, WEN Bo, WU Kun, LIU Si, XIAO Fuliang, ZHANG Aibin, XU Jiyao, ZHU Yajun

, Available online , doi: 10.11728/cjss2026.05.2025-0221

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Abstract:
This study investigates a nighttime medium-scale traveling ionospheric disturbance (MSTID) event observed over Fuke Station (19.5°N, 109.1°E) in low-latitude China on 8 December 2019, using airglow imaging and Digisonde observations from the Chinese Meridian Project’s Fuke Station, Global Positioning System (GPS) total electron content (TEC) measurements from Beihai Station (21.7°N, 109.2°E), and simulations from the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). The observations reveal typical northern hemisphere nighttime MSTID structures, characterized by alternating bright and dark bands with northwest–southeast-oriented bands propagating southwestward. During the propagating process, two dark bands exhibited a chasing phenomenon, in which the band that entered the field of view later caught up with the preceding band. The TIE-GCM was used to simulate the nighttime background neutral wind and electron density distribution. The simulation results suggest that the combined effects of spatial variations in the background zonal wind gradient and enhanced electron densities within the low-latitude equatorial ionization anomaly region were primarily responsible for regulating this chasing process. This study provides a theoretical basis for understanding how spatially nonuniform neutral winds and electron density distributions influence MSTID propagation.

Progress in Numerical and Laboratory Simulations of Ionospheric Irregularities

LEI Jiuhou, JIANG Konghan, LIU Yu

, Available online , doi: 10.11728/cjss2026.05.2026-0042

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Abstract:
The ionosphere contains plasma density irregularities with characteristic scales ranging from centimeters to hundreds of kilometers. These irregularities can induce rapid fluctuations, fading, and scattering in the phase and amplitude of radio waves propagating through the ionospheric medium, thereby having a significant impact on radio wave propagation characteristics. According to their latitudinal distribution, ionospheric irregularities are categorized into equatorial and low-latitude, mid-latitude, and polar types. Over the years, great progress has been achieved in both the observational and theoretical aspects of the characteristics of the ionospheric irregularities. Notably, the research group led by Professor Zuo Xiao of Peking University has carried out pioneering work in the observation, theoretical modeling, and even laboratory experiments of ionospheric irregularities. This article reviews the recent research progress made by the team of the School of Earth and Space Sciences, University of Science and Technology of China in the field of ionospheric irregularity simulations. The main topics cover numerical simulation studies of the terrestrial ionospheric irregularities at low, middle and high latitudinal zones and laboratory experiments of ionospheric plasma instabilities under partially ionized conditions. These studies systematically reveal the formation and evolution mechanisms of ionospheric irregularities in the middle and low latitudes, providing powerful tools for further investigation of related physical mechanisms.

Recent Rresearch Progress in Low-latitude Ionospheric Midnight Collapse of Electron Density

GONG Yun, CHEN Xinkun, MA Zheng, ZHANG Shaodong

, Available online , doi: 10.11728/cjss2026.05.2026-0027

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Abstract:
The low-latitude ionospheric midnight collapse is a typical structural variation in the nighttime evolution of electron density, reflecting vertical ion transport and its dynamical modulation in the nighttime ionosphere. Since the phenomenon was first observed, extensive studies have been conducted by the international scientific community to investigate its morphological characteristics and underlying physical mechanisms, using a variety of approaches including ground-based radar observations, satellite measurements, and numerical model simulations. This paper systematically reviews several decades of research progress on the low-latitude midnight collapse, with particular emphasis on its principal morphological features under different seasonal conditions and levels of geomagnetic activity. Focusing on the physical mechanisms, we highlight the dominant role of vertical ion drift in the formation and evolution of the midnight collapse and further analyze the key factors controlling variations in vertical ion drift. On this basis, future research directions for the midnight collapse and related nighttime ionospheric dynamical processes are discussed in light of recent observational and theoretical advances.

Construction Process and Measurement Progress of Qujing Incoherent Scatter Radar

DING Zonghua, WU Jian, YANG Song, DAI Liandong, XU Bin, MIAO Jiansu

, Available online , doi: 10.11728/cjss2026.05.2026-0003

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Abstract:
The Incoherent Scatter Radar (ISR) is the most powerful equipment for the ionosphere sounding on the ground. Some important events during the design and construction process of the Qujing ISR were described. Representative measurement results were introduced including the ionosphere, space debris and Moon measurement. The results show that this ISR can be used for the routine measurement of ionospheric electron density and plasma temperature in the fixed direction, the two-dimensional distribution in the scan mode, the abnormal structure of electron density, the bi-static receiving of the ionosphere. And it owns the ability of the space debris measurement with the size of more than 3 cm in the low Earth orbit in the beam parking mode, and the two-dimensional imaging and the scatter model correction of Moon. So Qujing ISR is of important value for the ionosphere and space environment measurement in China.

Polar Ionospheric TEC Inversion Based on Spaceborne Fully Polarimetric SAR and Its Response to Aurora

LI Changjun, XING Zanyang, WANG Cheng, YU Zhitong, ZHANG Qinghe, WANG Yong, MA Yuzhang, ZHAO Lingxin, LU Sheng, WANG Xiangyu, ZHAO Bianlong, AN Jiachen

, Available online , doi: 10.11728/cjss2026.05.2025-0244

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Auroral activity can enhance ionospheric Total Electron Content (TEC) at high latitudes and thereby affect the propagation of L-band electromagnetic waves transmitted by spaceborne fully polarimetric Synthetic Aperture Radar (SAR) systems. These ionospheric disturbances introduce additional phase delay and polarization distortion, which may reduce SAR data quality and influence the reliability of quantitative interpretation. Because the Faraday Rotation Angle (FRA) derived from fully polarimetric SAR observations is sensitive to the ionospheric electron content along the propagation path, it can be used to retrieve TEC with relatively high spatial resolution. In this study, 32 fully polarimetric SAR scenes were used to examine the performance of four FRA-based inversion algorithms for polar TEC retrieval under auroral conditions. The retrieved TEC was compared with colocated ground-based GNSS-TEC observations in order to evaluate the applicability of different algorithms in the polar ionosphere. In addition, two revisit SAR cases were selected to investigate how TEC enhancements related to auroral activity are reflected in SAR signal characteristics. This analysis makes it possible to assess both the relative performance of the four inversion methods and the response of polarimetric SAR observables to auroral ionospheric disturbances. Results show clear differences among the four algorithms. Of the tested methods, the Bickel and Bates (B&B) algorithm gives TEC estimates that agree best with the ground-based GNSS-TEC measurements, suggesting that it is more suitable for polar TEC retrieval. The revisit cases further show that TEC enhancements associated with auroral arcs can produce distinct changes in SAR observations. In regions affected by enhanced ionization, FRA increases noticeably, whereas the cross-circular polarization product decreases. These changes indicate a deterioration in SAR signal quality, especially a reduction in signal-to-noise ratio. Overall, the results indicate that fully polarimetric SAR, combined with an appropriate FRA inversion method, can provide useful information on polar ionospheric TEC and its disturbance characteristics during auroral activity. This approach offers a practical way to support high-latitude ionospheric studies and to examine the relationship between auroral processes and TEC variability.

Prospects for Scientific Research Based on Transit Observations of Earth by the Solar Polar-orbit Observatory

LI Hao, TIAN Hui, ZHANG Weihang, QIN Jianqi, YUE Xinan, HE Maosheng, YU Xizheng

, Available online , doi: 10.11728/cjss2026.05.2025-0237

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The Solar Polar-orbit Observatory (SPO) mission will employ a gravity assist of Jupiter to change its orbital inclination, enabling the spacecraft to leave the ecliptic plane and conduct direct imaging observations of the Sun’s poles. Before performing the gravity assist maneuver at Jupiter, SPO will orbit the Sun near the ecliptic plane, during which it will have the opportunity to observe the transit of the Earth across the solar disk in visible and Extreme-ultraviolet (EUV) bands. This paper focuses on the prospective Earth’s transit observations by SPO in the future and presents a preliminary assessment of the potential scientific investigations that could be carried out. First, the absorption of EUV radiation by the Earth’s atmosphere during transit can be used to retrieve the atomic oxygen number density in the thermosphere and its variation with altitude, thereby obtaining the vertical distribution of oxygen atoms. Using an empirical atmospheric model of Earth, we perform forward modeling of the absorption of EUV radiation by the Earth’s atmosphere. Inversion tests demonstrate that the absorption in these EUV wavelengths can be used to infer the distribution of atomic oxygen number density in the thermosphere within an altitude range of 250-600 km. Second, based on the characteristics of light curves in both the EUV and visible bands, obtained during the Earth’s transit, we can investigate the typical transit photometric signatures that may arise in future exoplanet transit detections in EUV bands. We simulate the light-curve characteristics during planetary transits in the EUV band. Due to the significant absorption of EUV radiation by planetary atmospheres, the resulting light curves exhibit characteristics that differ from those observed in the visible band. These results will provide important guidance and theoretical support for future EUV-based exoplanet detection missions.

Impact of Magnetospheric Substorm Evolution of a Multi-event on the Earth’s Outer Radiation Belt

TANG Chaoling

, Available online , doi: 10.11728/cjss2026.05.2025-0225

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The magnetospheric substorms play a crucial role in the dynamic processes of the Earth’s outer radiation belt. However, the specific influence of substorm evolution on the outer radiation belt remains insufficiently understood. This study investigates the effects of different substorm events on the outer radiation belt—specifically focusing on the enhancements of the source electrons (or chorus waves) and seed populations—by using joint observations from the THEMIS satellites and Van Allen Probes. Our analysis reveals the following key findings: The magnetic field dipolarization in the near-Earth tail, triggered by the substorm expansion phase, is a key process that facilitates the earthward injections of energetic electrons and ultimately affects the dynamics of the outer radiation belt. The activity level of chorus waves in the outer radiation belt is significantly modulated by the characteristics of substorm-injected electrons (the injected electron fluxes, durations, and pitch angle distributions) and shows a certain event dependence. The temporal structure of substorms (pulsed or continuous) significantly affects the response patterns of the outer radiation belt (single response or multi-stage response). These findings provide valuable insights for advancing our understanding of the dynamic processes of the outer radiation belt.

Coupled Ionosphere-Thermosphere Model for Spaceborne Intelligent Platforms

REN Zhipeng, YU Tingting, LI Shaoyang, WANG Yuhan

, Available online , doi: 10.11728/cjss2026.05.2025-0239

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Abstract:
With the development of space systems toward autonomy and intelligence, the traditional “space-sensed, ground-computed” model for space-environment support can no longer meet the needs of real-time response and autonomous decision-making. Aiming at the urgent demand of satellite platforms for real-time space-environment information, this study carries out an onboard-oriented reconstruction of the autonomous global ionosphere-thermosphere coupled model GCITEM-IGGCAS. Focusing on three major challenges encountered during in-orbit operation-system adaptability, computational efficiency, and real-time performance-this work implements several key upgrades, including adaptation and robustness enhancement of the operating environment, optimization of computational efficiency, and the construction of standardized data interfaces. Based on preserving the original physical core, the upgraded model significantly improves operational robustness, computational efficiency, and dynamic responsiveness across diverse onboard platforms. Simulation results demonstrate that the model can stably output key environmental parameters, such as thermospheric neutral density and ionospheric total electron content, whose spatial distributions are physically consistent. This indicates strong potential for providing real-time environmental inputs for tasks such as autonomous orbit management and enhanced communication and navigation. The study offers a feasible pathway for transforming high-end scientific models into intelligent onboard modules, and is of great significance for advancing “space-sensed, space-computed” capabilities.

Research Progress on Morphological Characteristics and Scintillation Effects of Equatorial Plasma Bubbles

ZHENG Yuhao, RANG Xinyi, GAO Shunzu, WAN Xin, XIONG Chao

, Available online , doi: 10.11728/cjss2026.05.2026-0068

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Abstract:
Equatorial Plasma Bubbles (EPBs) are among the most prominent plasma irregularities in the low-latitude ionosphere. Their multiscale morphological evolution and modulation of trans-ionospheric radio-wave propagation represent major scientific and practical concerns in space weather research. This review aims to summarize recent advances in the morphology, magnetic signatures, and scintillation effects of EPBs, and to identify key issues that require further investigation. Long-term in situ observations from low-Earth-orbit satellites, including CHAMP, GRACE, and Swarm, are reviewed together with complementary measurements from COSMIC radio occultation, ground-based Global Navigation Satellite System (GNSS) receiver networks, and all-sky airglow imagers. The occurrence characteristics of EPBs are first examined in relation to solar activity, geomagnetic activity, longitude, season, altitude, and local time. Previous observations demonstrate that EPB occurrence exhibits pronounced longitudinal and seasonal variability and is strongly controlled by the prereversal enhancement of the eastward electric field, background ionospheric conditions, and lower-atmospheric forcing. The spatial scales and three-dimensional morphology of EPBs are then discussed. EPBs are characterized by strong field-aligned extension, considerable zonal variability, and hierarchical structures ranging from large-scale plasma depletions to kilometer- and subkilometer-scale irregularities. Their morphology may evolve through upward growth, bifurcation, merging, and secondary instability development. Magnetic perturbations associated with EPBs are also reviewed. Available measurements suggest that their electromagnetic signatures may result from plasma diamagnetic effects, field-aligned currents, polarization electric fields, and Alfvénic perturbations. However, the relative contributions of these processes remain uncertain and require coordinated plasma and magnetic-field observations. Finally, the effects of EPBs on L-band signals are assessed, including amplitude and phase scintillation, signal fading, loss of lock, and positioning degradation. These effects depend not only on the large-scale geometry of plasma depletions, but also on the intensity and spectral distribution of embedded small-scale irregularities. Overall, EPBs should be regarded as multiscale, three-dimensional, and electrodynamically coupled ionospheric structures. Future progress will rely on coordinated multisource observations, improved three-dimensional reconstruction, and physics-based modeling. Such efforts are essential for understanding EPB evolution and improving the reliability of satellite communication, navigation, and positioning systems in equatorial and low-latitude regions.

Space Radiation Environment, Effects and Detection in Manned Space Missions

HE Pengzhi, SUI Li, HUA Daoben, WANG Zhimin, SHAO Changsheng, SHI Quanqi, JIA Xianghong

, Available online , doi: 10.11728/cjss2026.05.2025-0233

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As human space activities extend from low Earth orbit to the cislunar region and interplanetary space, space radiation has emerged as a fundamental safety issue constraining mission reliability and the feasibility of long-term human presence beyond Earth. Characterized by multiple sources, high particle energies, and strong temporal variability, the space radiation not only affects the reliability of spacecraft structural materials and electronic systems, but also poses potential risks to the physiological functions and long-term health of astronauts. In low Earth orbit, the radiation environment is primarily composed of trapped particle radiation, galactic cosmic rays, and sporadic high-intensity solar particle events. For deep-space exploration missions beyond the protection of the geomagnetic field, the spatiotemporal behavior and interaction mechanisms of space radiation become increasingly complex, exposing both spacecraft systems and astronauts to elevated radiation levels and cumulative effects. Meanwhile, long-duration missions involving extended habitation within spacecraft or extraterrestrial bases further amplify the effect of radiation on mission design and feasibility. This necessitates greater rigor in radiation monitoring, effects analysis, and risk assessment. To address these challenges, a systematic study integrating environmental characterization, radiation effects, and detection technologies is needed. This paper reviews the characteristics of the space radiation environment and its effects on both spacecraft systems and biological organisms. It further introduces the principles and current development of radiation detection technologies, including various dosimetric methods, particle identification techniques, and energy spectrum measurement approaches. In addition, representative space missions are examined as case studies to illustrate the evolution of radiation monitoring strategies and in-orbit measurement capabilities. Overall, this study provides a comprehensive review of the space radiation environment, its effects, and associated detection technologies in the context of human spaceflight. This study provides a scientific basis for radiation monitoring and risk assessment in manned spaceflight, and offers important references for safety analyses and mission design in deep-space exploration.

Multi-Instrument Observations of STEVE Evolution under Weak Substorm Conditions

WANG Jinghan, LI Shuhan, LIU Jing, LIU Shanbin

, Available online , doi: 10.11728/cjss2026.05.2025-0201

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STEVE (Strong Thermal Emission Velocity Enhancement) is a white/mauve optical arc in the subauroral region ionosphere that reflects the coupling among the ionosphere, magnetosphere, and thermosphere. A STEVE event on 16 April 2021 is analyzed using multi-instrument observations to investigate its morphological evolution and energy sources under relatively quiet solar wind and weak substorm conditions. By integrating optical observations from THEMIS all-sky imagers with ionospheric and magnetospheric measurements from GNSS TEC, the Swarm satellites, AMPERE field-aligned currents, NOAA POSE, and the Arase (ERG) spacecraft, we find that this STEVE event lasted for approximately 1.5 hours and evolved into Picket Fence structures. The STEVE region exhibited typical localized signatures of electron heating, electron density depletion, fast westward ion flow, and downward field-aligned currents. The elevated westward plasma velocity (about 4 km·s^–1), together with the unusually high electron temperatures (about 8000 K during STEVE), suggests that frictional heating associated with Subauroral Ion Drifts (SAIDs) alone cannot account for the observed thermal enhancement. Magnetospheric observations reveal broadband electron energy flux enhancements (dominated by <10 keV electrons), indicating that low-energy electron precipitation likely supplied additional energy to the STEVE region. This study demonstrates that, even during weak substorm periods, the combined effects of SAID and low-energy electron precipitation can substantially elevate electron temperatures in the subauroral ionosphere, thereby facilitating the formation of STEVE and Picket Fence structures.

Effects of Background Heavy Ions on Fast Magnetosonic Waves Excited by Proton-shell Velocity Distributions

WANG Ruohan, LIU Kaijun, MIN Kyungguk

, Available online , doi: 10.11728/cjss2026.05.2025-0228

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Fast Magnetosonic (MS) waves are frequently observed in the Earth’s inner magnetosphere and play a vital role in the acceleration of radiation belt electrons and the perpendicular heating of magnetospheric ions. They are generally believed to be generated via the proton Bernstein instability driven by proton velocity distributions with a positive gradient along the velocity component perpendicular to the background magnetic field. However, the effects of cool background heavy ions, such as helium ions and oxygen ions, on the instability remain insufficiently explored. The present study employs linear kinetic plasma theory to investigate how the concentrations of cool background helium and oxygen ions affect the growth rate, wave number, and unstable harmonic range of the proton Bernstein instability driven by proton-shell velocity distributions. The results show that increasing the concentrations of these heavy ions shifts the unstable waves toward larger wave numbers (corresponding to shorter wavelengths), reduces their overall growth rate, and moves the unstable harmonic range toward lower frequencies. These modulations of the proton Bernstein instability are more pronounced with the increase of the oxygen ion concentration than with that of the helium ion concentration. The reasons for these modulations are also discussed. First, the unstable waves approximately follow the cold plasma dispersion relation of MS waves which moves to larger wave numbers with the addition of heavy ions, leading to the wave number increase of the unstable waves. This also explains the overall growth rate reduction, because the most unstable waves tend to occur with wave numbers determined by the first peak of the squared Bessel function of the first kind involved in the growth rate calculation. This peak becomes farther away from the MS wave dispersion relation when the heavy ion concentrations increase. Finally, the heavy ion concentration increase comes with the background proton concentration decrease. Fewer background protons mean less damping on the lower harmonic modes, producing the shift of the unstable harmonic range toward lower frequencies. These findings improve the physical understanding of the excitation of not only MS waves in the Earth’s magnetosphere but also similar waves in heavy-ion-rich magnetospheres of other planets.

Derivation and Evaluation of Nighttime Zonal Wind in the Thermosphere Based on SYISR Observations

ZHANG Ning, YUE Xin’an, ZHOU Xu, CAI Yihui, WANG Junyi, WANG Yonghui, ZHU Yajun, DING Feng, NING Baiqi

, Available online , doi: 10.11728/cjss2026.05.2025-0199

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In our previous studies, using experimental data from Sanya (18.3°N, 109.6°E) Incoherent Scatter Radar (SYISR), we have obtained the line-of-sight ion velocity in multiple directions, subsequently calculated three-dimensional vector velocity through least square fitting, and finally derived electric fields from 200 km to 500 km based on the ion momentum equation. In this study, we further derived nighttime zonal wind from 200 km to 500 km based on the F region dynamo theory. To verify the reliability, we first analyzed the variations and errors of the nighttime zonal wind at different time scales. Then, we used an empirical model (HWM) and a theoretical model (NCAR-TIEGCM) for comparative analysis. Model results and observation results had a relatively good consistency. The maximum nighttime zonal wind velocity from the SYISR (HWM, TIEGCM) is 115.6 m·s^–1 (144.3 m·s^–1, 92.1 m·s^–1) for the monthly average value. We further compared the nighttime zonal wind from the SYSISR with that from a co-located FPI. They showed a positive correlation with a coefficient of ～0.68 for the zonal wind values, demonstrating a strong consistency between the two independent observation techniques.

Progress in Research on Mirror and Electromagnetic Cyclotron Instabilities of Multi-component Ions

MA Yuduan, YANG Youjun, AILIMU·Alimu, WANG Wei

, Available online , doi: 10.11728/cjss2026.05.2025-0176

Abstract(1136) FullText HTML (227) PDF 10652KB(158)

Abstract:
The mirror instability and Electromagnetic Ion Cyclotron (EMIC) instability, driven by ion perpendicular temperature anisotropy, are ubiquitous in space plasmas and play important roles in the evolution of substorms and storms. This paper outlines the physical mechanisms of these two instabilities based on Magnetohydrodynamics (MHD) and kinetic theory, and reviews the fundamental theoretical research results on the two instabilities under the condition of a single ion component (proton). EMIC waves are propagating waves below the proton cyclotron frequency along field-line resonances. In an electron- proton plasma, the waves are left-hand circularly polarized, or more generally left-hand elliptically polarized for propagation at an angle to the background field. In a multi-ion plasma, such as the magnetosphere, there are stop bands where no left-hand polarized waves are possible and bands where the waves are right-hand or right-hand elliptically polarized. Mirror modes are magnetic and plasma pressure fluctuations that are driven by proton temperature anisotropy instabilities. The wave magnetic pressure and plasma pressure are 180° out of phase with each other so there is a total pressure balance across the train of structures. Progress on the two types of instabilities in multi-component ions was further reviewed with a focus on exploring the impact of the heavy ions (He⁺,O⁺) in the terrestrial magnetosphere on these two types of instability. The theoretical derivation and numerical simulation related to instability thresholds and growth rates in multi-ion plasmas were summarized, and challenges in current research were analyzed including but not limited to non-Maxwellian ion distributions and nonlinear evolution of instability. To comprehensively reveal the regulatory effects of multi-ion components on these two types of instability and their significance in global kinetics, future research requires a combination of more systematic theories, advanced numerical simulations, and more satellite observations, which will provide important basis for a deeper understanding of energy transport and wave particle interactions in space plasma.

Propagation of Waves in the Middle and Upper Atmosphere Excited by Intense Events at the Earth’s Surface and in the Lower Atmosphere

XU Jiyao, YUAN Wei, LI Qinzeng, SUN Longchang, WU Kun, LIU Weijun

, Available online , doi: 10.11728/cjss2026.05.2025-0154

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Abstract:
Severe events at the Earth’s surface and in the lower atmosphere—such as volcanic eruptions, earthquakes, typhoons, thunderstorms, and anthropogenic explosions—can excite various types of waves. These waves propagate into the middle/upper atmosphere and ionosphere in the form of acoustic and gravity waves, exerting significant impacts on these regions. Such events provide typical case studies for investigating the physical mechanisms of coupling between Earth’s various spheres. This paper reviews the observational and research findings of Professor Xiao Zuo’s team regarding the effects of severe events like earthquakes and typhoons on the ionosphere. The paper also highlights the establishment of a dual-layer airglow observation network over China and the utilization of this detection system to study the propagation characteristics and effects of gravity waves excited by events such as volcanic eruptions, typhoons, and thunderstorms in the middle/upper atmosphere and ionosphere. The research results reveal that although gravity waves generated by volcanic eruptions cannot propagate directly over long distances in the middle and upper atmosphere, they can achieve extensive and long-range transmission through ocean-atmosphere interactions. The background atmospheric structure plays a crucial role in gravity wave propagation, with atmospheric waveguides enabling anomalous long-distance propagation of gravity waves. Although small- to medium-scale gravity waves have difficulty directly propagating upward to the thermosphere, secondary wave mechanisms can effectively facilitate their propagation from the middle atmosphere to the upper atmosphere. Furthermore, studies on typhoon events provide direct observational evidence of how severe lower atmospheric events influence the upper atmosphere and ionosphere.

Review of the Development of the In-Satellite Particle Detector for the China-Brazil Earth Resources Satellite-1

ZOU Hong, ZHONG Weiying, HAO Yongqiang

, Available online , doi: 10.11728/cjss2026.05.2025-0164

Abstract(913) FullText HTML (188) PDF 11263KB(147)

Abstract:
The In-Satellite Particle Detector onboard the China-Brazil Earth Resources Satellite-1 (CBERS-1) was the first space particle radiation detection payload developed by the project team at Peking University. The main objective of this payload was to monitor the high-energy electron and proton radiation environment inside the satellite. The payload probe consists of an electron probe and a proton probe. The electron probe is a ΔE-E telescope composed of a 100 um-thick silicon surface barrier detector and a 5000 μm-thick lithium drift detector, capable of measuring electrons ranging from 0.5 to 2.0 MeV and above 2.0 MeV, while eliminating proton contamination. The proton probe is a telescope consisting of two silicon surface barrier detectors with thicknesses of 100 μm and 450 μm respectively, capable of measuring protons ranging from 5 to 30 MeV and 30 to 60 MeV. From the task assignment in 1987 to the delivery of the flight-mode payload in 1998, the development process underwent four stages: principle-mode, electrical-mode, qualification-mode, and flight-mode, spanning over 11 years. On October 14, 1999, the CBERS-1/01 satellite was successfully launched. The In-Satellite Particle Detector was powered on three days later and successfully transmitted data, and then operated normally in orbit until the end of the satellite's lifespan. After preprocessing the payload’s data and matching it with satellite orbit information, the data suitable for scientific research was obtained. The data analysis proved that the In-Satellite Particle Detector performs well in orbit, and its observations are in accord with expectations. Based on the payload’s data, several papers on radiation belt research have been published. The successful development of the In-Satellite Particle Detector onboard CBERS-1 marks a milestone in the development of space particle detectors by Chinese universities, and lays a solid foundation for the subsequent development of space detection payloads at Peking University.

An Ionospheric Space-Weather Data Assimilation System over China Based on Meridian Project GNSS Measurements

A Ercha, LUO Xinyue, CHEN Yanhong, SHEN Hua, YUAN Tianjiao, HUANG Wengeng, WANG Xin, LU Guorui, LUO Bingxian

, Available online , doi: 10.11728/cjss2026.05.2025-0182

Abstract(1386) FullText HTML (224) PDF 12305KB(195)

Abstract:
The successful deployment and national acceptance of the second phase of the Chinese Meridian Project (CMP), a major national scientific and technological infrastructure, signify a substantial leap forward in China’s space environment monitoring capabilities. In particular, CMP’s ionospheric monitoring network has greatly strengthened both research and operational capabilities in ionospheric space weather. This study presents a new-generation ionospheric space weather data assimilation system for China and adjacent regions, based on GNSS observations from the CMP. Leveraging stable and robust data from 85 GNSS stations from CMP and the International GNSS Service, the system integrates multi-constellation GNSS measurements from GPS, GLONASS, BeiDou, and Galileo as input and employs a three-dimensional variational assimilation approach. It generates high-precision and operational ionospheric space weather products, represented by ionospheric TEC, covering China and adjacent regions (15°－55°N, 70°－140°E), which significantly improves the ability to reconstruct and characterize ionospheric disturbances over China. This data assimilation system can provide diverse ionospheric space weather products, including gridded TEC, ΔTEC, and the Rate of TEC change Index (ROTI), with a high spatial-temporal resolution of 1°×1°×15 min. These ionospheric products are routinely updated and publicly available via the website of the Space Environment Prediction Center (http://www.sepc.ac.cn/TEC_chn.php) at the National Space Science Center, Chinese Academy of Sciences. Beyond enabling high-fidelity monitoring of the ionospheric space environment over China and adjacent regions, this system also supports in-depth investigation of multi-scale ionospheric variations and irregularity characteristics. In addition, it delivers timely, accurate, and effective ionospheric space weather information and error correction for shortwave communication, radar imaging, satellite navigation, and space weather nowcasting.

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