空间科学学报

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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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Abstract:
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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Abstract:
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

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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(845) FullText HTML (136) 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(1316) FullText HTML (166) PDF 12305KB(192)

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.