Previous research has established that in geospace, the total electron content (TEC) in the ionosphere can be modulated efficiently by ultralow frequency (ULF) waves in high-latitude regions. However, the correlations between TEC variations and ULF waves in middle-latitude and low-latitude regions remain inadequately explored. In this study, using ground-based magnetometer data from the Chinese Meridian Project, we identified ULF wave events within Pc4 frequency bands in the midlatitude region. During the period from 1 July to 30 December 2023, we identified 642 distinct ULF wave events in the Pc4 band, thereby creating a comprehensive ULF wave database. Statistical analysis indicated that Pc4-band ULF wave events predominantly occurred on the night side in midlatitude regions. Notably, on 24 August 2023, simultaneous observations of geomagnetic disturbances and TEC disturbances at a similar frequency were recorded, suggesting a potential correlation between Pc4 ULF waves and TEC variations at midlatitudes. Through quantitative analysis, we infer that ionospheric TEC variations were triggered by Pc4 ULF waves during this event and the mechanism underlying this may be the horizonal plasma density gradient. This result provides direct observational evidence of the modulation of the TEC by Pc4 ULF waves in the midlatitude region. Furthermore, multiple additional TEC modulation events associated with ULF waves were identified, substantially reducing the likelihood of coincidental occurrence and reinforcing the validity of our findings. These findings broaden our understanding of the coupling between the solar wind-magnetosphere-ionosphere in midlatitude regions, and may be significant for evaluating the effect of space weather of this coupling process.

Enhancements of large‐scale convection electric fields in the inner magnetosphere, likely linked to low‐latitude penetration electric fields in the ionosphere, are key components of solar wind–magnetosphere–ionosphere coupling. These fields reflect large‐scale magnetosphere convection induced by the solar wind and are known to influence various geomagnetic indices such as Kp, AU, and Dst. In this study, we examine large‐scale electric fields observed by the Van Allen Probes, along with solar wind conditions and geomagnetic indices, during 191 isolated high‐speed solar wind events from October 2012 to August 2019. We find that the strength of the electric field within L‐shells less than 5.5 increases with both solar wind speed and the southward component of the interplanetary magnetic field. Superposed epoch analysis reveals that the penetration depth of the convection electric field increases with solar wind speed. When solar wind speed exceeds 550 km/s, significant electric fields reach . Statistical analyses show that the Kp, AU, and Dst indices exhibit an approximately linear relationship with electric field strength when . Above this threshold, these indices exhibit a slower rate of increase, indicating a nonlinear response of geomagnetic indices to stronger convection electric fields. Additionally, AU correlates approximately linearly with Kp, while Kp shows a roughly logarithmic relationship with Dst. These results confirm that magnetospheric convection significantly influences Kp, AU, and Dst, particularly under high‐speed solar wind conditions.

Charged particle precipitation typically manifests as a gradual increase and decrease of flux observed by space detectors. Cases with rapid flux variation are very rare, while periodic events are even more extraordinary. These oscillating particle precipitation (OPP) events are usually attributed to the bounce motion of electrons probably induced by lightning. However, the origin of these oscillation events is still on debate. Here we report three peculiar charged particle precipitation events detected by GECAM during a geomagnetic storm on March 21, 2024, with two exhibiting significant periodicity. These events were observed around the same region during three consecutive orbits with a life time of more than 3.5 h. Through comprehensive temporal and spectral analyses, we find that one of the OPP events exhibited a transition in spectral lag of mini-pulses, shifting from “softer-earlier” to “softer-later” while showing no significant time evolution in overall frequency characteristics, and that there is no association found between these two OPP events and lightning activity nearby. Finally, we discussed possible scenarios to explain these GECAM-detected OPP events, and we found that they may represent a new type of particle precipitation event or a peculiar lightning-induced electron precipitation (LEP).

The Earth's outer radiation belt is highly dynamic, containing relativistic electron fluxes that can increase by several orders of magnitude during magnetospheric disturbances. This greatly increases the likelihood of spacecraft malfunction or failure and significantly influences the solar-terrestrial system's energy and mass coupling, highlighting the importance of fully understanding the mechanisms governing these dynamics from both theoretical and practical perspectives. Although many theories have been proposed, further research is essential to quantify the specific contributions of different dynamic mechanisms for improving space weather forecasting. To address this, observations of the outer radiation belt with high spatial-temporal resolution to distinguish the spatial and temporal variations are essential. We introduce a 10-CubeSat constellation survey scheme in the geosynchronous transfer orbit (GTO) to achieve this required observation. Three baseline instruments are proposed to be employed: the high energy electron detector (HEED), the search coil wave detector (SCWD), and the magnetometer (MAG). Two groups of physical processes will be investigated: wave-particle interactions involving charged particles interacting with whistler-mode waves, electromagnetic ion cyclotron (EMIC) waves, and ultra-low frequency (ULF) waves; and radial transport encompassing shock-induced injections, substorm injections, storm convection and magnetopause shadowing. The performance parameters of instruments and platform of the constellation are presented. Additionally, aligned with the concept of constellation survey, we outline the COSPAR-coordinated space program, COnstellation of Radiation BElt Survey (CORBES), which will provide a crucial scientific contribution in the absence of the Van Allen Probes. The program's excellent obser-vational capability enables a comprehensive understanding of the underlying physical mechanisms governing the outer radiation belt dynamics and improved space weather forecasting. (c) 2024 COSPAR. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).

On 10 May 2024, near-Earth space experienced the most intense geomagnetic storm in nearly two decades, accompanied by extreme substorms and rare low-latitude auroral displays observed in regions such as Beijing and Altay. Geomagnetic storms and substorms are explosive manifestations of solar wind-magnetosphere coupling and are key drivers of space weather. Understanding these phenomena remains a fundamental challenge for space weather forecasting. This article reviews recent progress in storm-substorm research, focusing on internal processes of storm-substorm such as magnetospheric convection, magnetic reconnection, electric current systems, auroras, and energetic particles. Despite significant progress, the way these physical processes are connected across different regions-and the intrinsic relationship between storms and substorms-remains unclear. Inspired by Earth system analogies, such as mantle convection driving plate movement and atmospheric convection causing extreme weather, we propose a new conceptual framework centered on the evolution of magnetospheric convection for future studies of stormsubstorms. The core hypothesis is that magnetospheric convection, through the motion of frozen-in magnetic field lines, reorganizes large-scale current systems and ultimately governs the development of storms and substorms. This main hypothesis is mainly motivated by following considerations. From the perspective of magnetohydrodynamics (MHD), magnetic field lines and plasma are frozen together and convect as a single entity on macroscopic scales, with only a few exceptions at small scales, e.g., diffusion region of magnetic reconnection. As a result, convection inherently drives the global-scale evolution of magnetic field lines. Within the MHD framework, convection is the primary mechanism capable of restructuring magnetic fields, forming thin current sheets, and building up current systems in the magnetosphere. This can occur directly through the stretching of field lines, or indirectly through the injection of energetic particles that enhance current intensity. The framework in which magnetospheric convection drives the space current system is broadly consistent with existing observations and theoretical models. For example, both cross-tail currents and ring currents-key components of substorm and storm current systems-are influenced by magnetospheric convection. This perspective offers a possible way to connect various physical processes involved in storms and substorms, helping to reveal the relation between them within a unified framework. Based on this framework, we outline three key scientific questions: (1) how does magnetospheric convection evolve during substorms, and how do the electric current systems respond? (2) What happens to magnetospheric convection and the corresponding current system during storms? (3) What is the intrinsic link between storm-time and substorm-time convection? This framework can be summarized as "one core hypothesis, three key scientific questions, and eight physical processes of storm-substorm". As an initial application of this framework, we discuss the possible cause of the unusual low-latitude auroras during the May 2024 storm, suggesting that they may result from extreme magnetospheric convection driving large-scale field-aligned currents that expand equatorward in the ionosphere. From the perspective of storm-time convection, the significant equatorward expansion of the auroral oval during the extreme May 2024 geomagnetic storm reflects an overall intensification of magnetospheric convection and its deeper penetration into the inner magnetosphere. Within the magnetosphere, the enhanced convection electric field leads to plasmasphere erosion and drives field-aligned currents deeper into lower L-shell regions. From the ionospheric viewpoint, continuous dayside magnetic reconnection opens previously closed magnetic field lines, pushing the open-closed boundary equatorward. This process causes the entire high-latitude current system to shift toward lower latitudes. Accompanied by these field-aligned currents, aurora-related precipitating electrons also reach lower L-shells, and through magnetic field line mapping, affect the low-latitude ionosphere. Comprehensive studies on the storm and substorm from perspectives of magnetospheric convection are still in an early stage. Forthcoming missions like SMILE (Solar-wind-Magnetosphere-ionosphere Link Explorer) and future multi-scale magnetosphere CubeSat constellation missions like AME (self-Adaptive Multi-scale magnetosphere cubeSat constellation) will provide valuable observations to test this framework. These will help us improve our understanding of how storm and substorm develop.

Rapid relativistic electron enhancements (REE) in the outer radiation belt have long been an intriguing phenomenon for space weather. In this study, we investigate rapid REE from October 2012 to December 2017 using multi-spacecraft observations. A total of 27 rapid REE events are identified from the Van Allen Probes (RBSP) measurements with a 5 times increase of MeV electrons at the center of the outer radiation belt (L = 4.5-5.5) in a half RBSP orbit (similar to 4.5 hr). All REE events are found to be in association with pulse-like injections of MeV electrons in the outer radiation belt. Electron fluxes in each injection at L similar to 6.6 and the overall electron enhancements at L = 4.5-5.5 are quantified. The 500 keV and 0.8-1 MeV electron fluxes are correlated in injections and in overall enhancements. Substorm strength is more intense before/during the REE than intervals after the REE. The statistical study suggests that substorm-associated MeV electron injections are highly correlated with rapid REE in the outer radiation belt. Rapid relativistic electron enhancements (REE) in the outer radiation belt are one of the most important phenomena in space weather. The fast increases of MeV energy electrons can have significant impacts on satellite operations and safety. In this study, we identify 27 events of relativistic electron enhancements in which MeV electron increases five times in similar to 4.5 hr at a radial distance of 4.5-5.5 Earth radius. All REE events are found in association with multiple pulse-like injections of MeV electrons. The electron fluxes during each injection at geosynchronous altitude and the overall enhancements in the center of the radiation belt are quantified. The increases in sub-relativistic and MeV electron fluxes are highly correlated. Overall, this research provides insights into the correlation between substorm-associated MeV electron injections and the rapid intense REE in the outer radiation belt, contributing to a better understanding of the dynamics and processes involved in the radiation belt particle energization. All 27 events of rapid enhancement of relativistic electrons are found to be associated with injections of MeV electrons The 500 keV and 0.8-1 MeV electron fluxes are highly correlated during injections at L similar to 6.6 and in overall enhancements at L = 4.5-5.5 Substorm strength is more intense during rapid relativistic electron enhancements

A COnstellation of Radiation BElt Survey (CORBES) program is proposed by the Sub-Group on Radiation Belt (SGRB) of TGCSS, COSPAR. To address the open qustions about the dynamics of the Earth’s radiation belt, CORBES mission would use a constellation of small/CubeSats to take an ultra-fast survey of the Earth’s radiation belt. The concept, science objectives and preliminary technical design of CORBES are introduced. This mission is an international multilateral cooperation mission coordinated by COSPAR. The SGRB Science Activities and COSPAR HQs Coordinate Activities on CORBES are summaried.

A COnstellation of Radiation BElt Survey (CORBES) program is proposed by the Sub-Group on Radiation Belt (SGRB) of TGCSS, COSPAR, which is in pursuit of the goal of SGRB, focusing on the implementation of a Small/CubeSats constellation mission for radiation belt exploration. Basing on a general review of the status quo of research on the Earth’s radiation belts dynamics and the unresolved scientific issues, the scientific object and observation requirements of CORBES are proposed. The CORBES program is expected to have a constellation of 10-plus small/ CubeSats to take an ultra-fast survey of the Earth’s radiation belt. The general science goal for CORBES is to investigate two groups of physical processes related to the radiation belts: wave-particle interactions and radial transport. This program is an international multilateral cooperation mission, an open and sharing data policy will be implemented. The data set of observations will be shared within the contributors of the constellation and the broad research community at large, then would be of great use for comprehensively understanding the dynamics of magnetospheric energetic populations and developing more standard models of the Earth’s radiation belts. Furthermore, from the application perspective, the ultra-fast survey of the radiation belt could serve as an important facility for monitoring space weather of the Earth as well.

Understanding the radiation belts comprehensively has prominent significance both for aerospace engineering and space weather. For both the development of radiation belts models and the research into the dynamics of energetic electrons in the inner magnetosphere, the availability of global, well cross-calibrated data is crucial. In this report, we carry out an on-orbit cross-calibration between the observations from the High Energy Electron Detector (HEED) on Bei Dou navigation satellite system (BD) of China and Combined X-ray and Dosimeter (CXD) on Global Positioning System (GPS) constellation using the relativistic electron flux data from 2012 to 2014 and obtain the systematic offsets between the two systems. The fitting results show that there is a good consistency with the electron observations from M04 and ns63 with linear fitting slopes between relativistic electron fluxes from HEED and CXD all near 0.9. Using the cross-calibration results, the observations of greater than 1 MeV electrons of M04-HEED and GPS-CXD are assimilated well by removing the system deviation. Taking advantage of assimilated electron observations from M04 and ns63, the evolution of electron energy spectrums during the two sequential magnetic storms in March 2013 is investigated. Different dynamic properties presented by assimilated observations suggest different physical process dominant during these storms. Furthermore, this case study demonstrates the significance of the cross-calibration between M04 and ns64 observations and the usefulness of assimilated observations. This work is the first try to show that the relativistic electron observation from BD is compared with the same type operational satellite GPS. It could be expected that huge assimilated observations using the cross-calibration presented in this work would be extremely useful for statistical radiation belt modeling research, space weather nowcasting and forecasting, and comprehensive scientific understanding of energetic electron dynamic processes in the radiation belts. (c) 2022 COSPAR. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).

为降低真空环境下产品的控温风险,以热真空试验的控温系统为研究对象,分析串级PID温度控制原理,在串级PID控制算法基础上进行多分区及参数自整定,提出一种适用于大滞后性系统的产品控温方法.试验验证结果表明,应用此控温方法对某卫星功率放大器热真空试验进行控温,实现了较高的精度(达到±0.5?℃)和较小的超调量(仅0.7?℃),升、降温速率≥1.5?℃/mm.

Abstract Using magnetic field observations from Van Allen Probe‐A (VAP‐A), we evaluated the performances of 13 widely used external magnetic field models in the Earth's outer radiation belt region in detail. It is shown that later models tend to match observations better than earlier models except for T03s, which has a top performance similar to the latest TA16_RBF model. Additionally, in its applicable domain from quiet to moderately disturbed geomagnetic conditions, T02 has comparable performance to T03s. In the dusk, dawn and night sectors, highly stretched magnetic fields are seen in both the observations and model output between LmIGRF ∼5.7 and 6.1, which suggests the existence of steep radial gradients in the plasma pressures inside the outer belt region. The contributions from the currents located in the dusk sector during a disturbed period, such as the partial ring current and the substorm current wedge, are not adequately accounted for by the models, and the contribution of field‐aligned currents may also be underestimated. The results of this study will help select reliable external field models for future radiation belt studies and help assess uncertainties caused by the selected models. In addition, detailed analysis of the field components depicted by the empirical models could shed light on understanding the contributions from different current systems in this region.

Accuracy of geomagnetic field model has key importance for the theoretical and operational studies about radiation belt. Using magnetic field data measured by Van Allen Probes (VAP) from 2012 to 2018 and GOES15 from 2011 to 2017, this paper quantitatively evaluates performances of three newer empirical external magnetic field models (TS05, TA15, and TA16) in the outer radiation belt (3 similar to 6.6R(E)). The prediction efficiency (PE) is chosen as a measure to quantitatively assess models' performance in various spatial ranges (Lm), under different geomagnetic conditions (Kp), and along with magnetic local time (MLT). Also, theta (the angle between the observed and estimated magnetic field vector) is calculated to evaluate the model's ability to predict the direction of the magnetic field. The results show that with increasing Lm and disturbed level of geomagnetic field, the PE decreases and the 0 increases. The PE at MLT=12-21 is smaller than MLT = 0 - 9 in the range of Lm = 5 similar to 6.5R(E), showing a dawn-dusk asymmetry and indicating that the three magnetic field models can describe the strength of the magnetic field in the dawn sector better than in the sector from afternoon to dusk; at the geosynchronous orbit (Lm similar to 6.6R(E)), PE at MLT=9-15 is greater than at other local times, the day-night asymmetry indicates that the three magnetic field models can well estimate the magnitude of the magnetic field in the dayside, but they may have noticeable errors on the nightside. The theta at MLT = 6 - 12 is smaller than at other local times, showing a day-night asymmetry and indicating that the three magnetic field models can better describe the geomagnetic field configuration in the dayside, but they may have noticeable errors in the nightside. Within the range of Lm similar to 3 similar to 6.5RE, the estimations of TA16 are the closest to the observations from VAP, with PE>0.7 and theta<3 degrees; at the geosynchronous orbit (6.6R(E)), the estimation of TS05 model is the closest to the observations from GOES15 with PE of about 0.75 and theta of about 7 degrees. The relevant research results can provide references for the selection of geomagnetic field models for the on-orbit cross calibration of energetic particles for Chinese spaceborne energetic particle detectors, the study of the dynamic model of energetic particles in the radiation belt, and related theory/application research of the magnetospheric environment.

Magnetospheric relativistic electrons can destroy on-orbit spacecrafts completely by internal charging and discharging effects. As the characteristics and physical mechanism of this space particle are still unclear, magnetospheric relativistic electrons have always been an important object of space environment exploration and space science research. For studying the physical mechanisms and developing models relating to magnetospheric relativistic electrons, it is necessary to use the observations from different satellites and detectors at the same time. Eliminating the systematic deviation between different detection systems to assimilate the observations from different sources is essentially required by such researches. In this work, the on-orbit cross-calibration and assimilation for relativistic electron (> 2 MeV) observations from FengYun 4A and GOES-13 are performed. In this work, only the observations obtained under very quiet geomagnetic conditions (Kp < 2) are adopted to ensure that the objects of study are the radiation belt particles, which are stably captured by the geomagnetic field. According to the physical characteristics of the radiation belt particles, that is, the three adiabatic invariants, and based on the Liouville theorem, the phase space density of the stably captured particles is unchanged. In this paper, the relativistic electron flux data of energy > 2 MeV and instrument pitch angle are in the east and west direction respectively. If the particles’ energy is the same, then their corresponding μ values are the same, and their particles’ directions are the same, then their corresponding J values are the same, and the Liouville theorem can be simplified as the drift shell Lm is the same, the fluxes are the same, and the electron fluxes observed by the two satellites are compared in the drift shell Lm coordinate. The systematic deviation between the two satellites’ relativistic electronic observations can be obtained. According to this result, the data assimilation is carried out, and the results show that the system deviation can be removed well. By this research work, the systematic deviation between two important relativistic electron detection systems in geosynchronous orbit is obtained. Based on the obtained systematic deviations, the assimilations for observations from the two detection systems are achieved. This work lays a solid foundation for the follow-up theoretical and applied researches, and also provides the methods for on-orbit cross-calibration and observation assimilation which could be referred to when other electronic observations on geosynchronous orbit are dealt with.

Using multisatellite measurements, a uniquely strong and long-lived relativistic electron slot region refilling event from November 2004 to January 2005 is investigated. This event occurred under remarkable interplanetary and magnetospheric conditions. Both empirically modeled and observationally estimated plasmapause locations demonstrate that the plasmasphere eroded significantly prior to the enhancement phase of this event. The estimated diffusion coefficients indicate that the radial diffusion due to ULF waves is insufficient to account for the observed enhancement of slot region electrons. However, the diffusion coefficients evaluated using the distribution of chorus wave intensities derived from low-altitude POES electron observations indicate that the local acceleration induced by chorus could account for the major feature of observed enhancement outside the plasmapause. When the plasmasphere recovered, the refilled slot region was enveloped inside the plasmapause. In the plasmasphere, while the efficiency of hiss scattering loss increases by including unusually low frequency hiss waves, the interaction with hiss alone cannot fully explain the decay of this event, especially at higher energies, which suggests that electromagnetic ion cyclotron waves contribute to the relativistic electron loss process at such low L shells for this refilling event. Through a comprehensive analysis on the basis of data analyses and numerical calculations, the present study sheds light on the underlying physics responsible for the unusual slot refilling by relativistic electrons, which exhibits the complexity of both radiation belt electron dynamics and associated wave-particle interactions.

对地球同步轨道空间辐射环境监测及应用进行了研究.给出了持续开展的国外GOES系列卫星和国内FY-2系列卫星的地球同步轨道空间粒子辐射探测介绍,以及AE8和AP8、AE9和AP9、POLE、FLUMIC等用于地球同步轨道带电粒子辐射环境评估的经验模型发展.我国自主高能带电粒子辐射监测自20世纪90年代中后期开始,FY-2系列卫星上的带电粒子探测仪器经过了两代卫星的技术巩固和第三代卫星的创新发展,实现了更精细的能道划分并拓宽了对带电粒子辐射能谱的探测.介绍了用FY-2系列卫星获得的不同扰动状态下高能电子能谱特性,兆电子伏特级高能电子快速、缓慢增强事件,以及与GOES-13,15卫星联合应用分析高能电子不同地方时动态与太阳质子事件动态演化结果.用FY-2系列卫星获得的观测数据能准确、灵敏反映轨道空间高能带电粒子的动态变化;与GOES系列卫星的同期观测结果比较既反映出相对平静时的趋于一致性,又反映了强扰动下的显著短时局地差异,这为开展该轨道粒子辐射实测数据多星联合分析,发展磁层对扰动响应更全面、更复杂的图像,为带电粒子起源、重新分布、损失机制等深入研究提供了可能.在最新的第一代静止气象卫星FY-4卫星上,带电粒子探测仪器兼顾了能谱和方向的设计,既具备FY-2系列卫星平台高能电子、质子全能谱的探测,又增加了高能电子的多方向探测.目前除GOES系列卫星以外,仅有我国地球同步轨道系列卫星可提供持续的轨道空间粒子辐射环境长期实测记录,数据的长时间积累和信息丰富将促进地球同步轨道空间粒子辐射经验模型向更精细化的方向发展,并推动我国空间粒子辐射环境理论和自主建模研究,更好地服务于我国空间天气监测预警业务.

By utilizing data obtained on Chinese satellite in the middle Earth orbit from solar activity descending phase to solar activity ascending phase, the properties of high energy electron environment in the middle Earth orbit are analyzed, such as spatial distribution, flux intensity, temporal variations, and response to geomagnetic storms. The investigating results indicate that the spatial distribution of high energy electron in the middle Earth orbit is stable; the fluxes of electrons decrease with energy increasing; the high energy electron environment is a dynamical system which disturbs evidently on different timescales; the evolvement of this system is stimulated by geomagnetic storms, but the correlation between the evolvement and the storms is nonlinear.