When the interplanetary magnetic field (IMF) changes towards its final orientation, induction within the Moon enhances the magnetic field beneath the lunar surface but outside the conductive interior. This enhanced magnetic field compresses the solar wind near the lunar terminator, forming limb compression structures. Using three-dimensional, time-dependent magnetohydrodynamic simulations, we systematically explore how the lunar core radius, core conductivity, and the amplitude of the IMF variation influence these limb compression structures. Our findings demonstrate that a larger core radius, higher core conductivity, and a larger magnetic field change result in a stronger induced magnetic field and more pronounced limb compression. However, when core conductivity exceeds 0.1 S m(-1), further increases in the core conductivity have minimal impact. These simulation results serve as a forward-modelling study that lays the groundwork for future efforts to constrain the lunar interior stratification under conditions of external magnetic field perturbations by combining numerical modeling with spacecraft observations.

This paper presents the second generation of the China Seismo-Electromagnetic Satellite (CSES) Global Geomagnetic Field Model (CGGM-2), specifically designed to derive candidate models for the fourteenth generation of the International Geomagnetic Reference Field (IGRF-14). To build this CGGM-2 model, we utilize more than six years of geomagnetic field data collected by the high-precision magnetometer (HPM) onboard CSES. The model is parametrized by expanding the internal field to spherical harmonic degree and order 45, now incorporating lithospheric contributions. This was not the case for the first generation CGGM model, which was limited to spherical harmonic degrees up to 15. We now also implement order six B-splines in time with one year knot spacing for degrees 1 to 13 to capture non-linear temporal variations in the core field, superseding the linear approximation used in CGGM. Despite a number of challenges, such as boom deformation on which the HPM is located (away from the star imager that provides attitude information) and high-latitude magnetic field platform disturbances, the CGGM-2 model succeeds at capturing the non-linear temporal variations of the geomagnetic field. In particular, the SV-2025-2030 candidate model derived from CGGM-2 performs particularly well among all 18 candidate models for IGRF-14. Candidate models derived from the CGGM-2 are also the only IGRF-14 candidate models using CSES data only and not directly relying on any ESA’s Swarm satellite data, thus providing useful candidate models to compare against all other IGRF candidate models. Our findings underscore the potential of CSES data for geomagnetic field modeling and the likely benefits of CSES’s revisiting capability for accurately capturing the main field's variations. It is expected that future data from the forthcoming companion CSES-02 mission will help improve the temporal–spatial resolution of the model and mitigate high-latitude magnetic platform disturbances.

Macau Scientific Satellite-1 (MSS-1) is a low-Earth orbit (LEO), low-inclination satellite mission launched on May 21, 2023. Its primary scientific objectives are to separate geomagnetic sources and characterize magnetic fields near the Earth's surface. To achieve these goals, high-quality vector magnetic data were obtained through rigorous preflight and in-flight calibration procedures. This study outlines the key workflow for magnetic data processing, as well as the format, naming conventions, and content of the data products, which serve as valuable references for scientific research. For orientation calibration, an attitude combination method was developed and implemented, achieving a weighted standard deviation of approximately 1.5 arc sec for the inter-boresight angle between combined quaternions and quaternions from three cameras of star tracker. Additionally, a joint estimation approach was employed that combined Euler angles and geomagnetic field model coefficients. To evaluate the quality of the data, comparisons were conducted between MSS-1 and the Swarm satellite to capture typical space magnetic disturbances. Closest to the orbital intersections, the results indicate a maximum difference of approximately 3 nT in the vector components, observed under various conditions. Consistency in describing geomagnetic storms was also demonstrated between MSS-1 data and specialized geomagnetic indices, with correlation coefficients greater than 0.91 for all cases. It can be concluded that the vector magnetic data products generated by the MSS-1 processing workflow are of high quality. This workflow is adaptable for use in the upcoming MSS-2 mission or other nonpolar LEO satellite missions.

The Macau Science Satellite-1 (MSS-1) is the first space science satellite jointly developed on the Chinese mainland and in Macau. It comprises two satellites, named MSS-1A and MSS-1B, and holds considerable importance in China’s space exploration endeavors. Among these, MSS-1A is the world’s first high-precision scientific satellite dedicated to exploring the geomagnetic field and space environment at low latitudes. Equipped with two high-precision vector magnetometers and one scalar magnetometer, which are integrally installed on a highly stable nonmagnetic optical bench, the MSS-1A enables simultaneous high-precision measurements of both the Earth’s vector magnetic field and its scalar components. Its design integrates several state-of-the-art technologies, including arc-second-level thermal stability control, nonmagnetic thermal control for the optical bench, and ultra-high magnetic cleanliness control. These innovations effectively minimize magnetic interference originating from the satellite itself, thereby substantially improving the precision of geomagnetic field measurements and establishing a robust technical foundation for future magnetic survey satellite constellations.

Although the Moon lacks a global dipole magnetic field, widespread crustal magnetic anomalies preserve critical information about the origin and evolution of its ancient magnetic field. These anomalies are closely related to the interaction between the solar wind and the lunar surface, the Moon’s thermal history, the formation of mini-magnetospheres, and the structure of the deep interior. Since the Apollo missions, multiple space-craft-such as Lunar Prospector and Kaguya-have provided extensive measurements of the lunar magnetic field. Based on the information obtained from the above missions, a variety of methods for mapping and modeling the crustal magnetic field have been developed. This paper reviews magnetic anomaly mapping using electron reflectometer data and summarizes the progress and challenges in high-resolution modeling based on vector magnetometer data. We summarize the standard workflow for vector-based magnetic field mapping and modeling: (1) selection of magnetically quiet periods; (2) removal of external field contributions; (3) altitude normalization; (4) suppression of instrumental and environmental noise; and (5) model inversion and magnetic field mapping. Key methods and models employed in each step are discussed in detail, with a comparative analysis of their strengths and limitations based on existing studies. The modeling of the Moon’s crustal magnetic field is relevant to fundamental scientific questions about its geologic and magnetic evolution and is expected to play an increasingly important role in future lunar exploration and scientific investigations.

On July 27, 2022, a high-precision system for measuring the magnetic field based on a coherent population trapping magnetometer (referred to as the CPT system) was launched onboard the Space Advanced Technology demonstration satellite (SATech-01) by a ZK-1A rocket. The payload comprises a scalar coherent population trapping magnetometer (CPTM), triaxial anisotropic magnetoresistance magnetometer (AMRM), and nano star tracker mounted on a non-magnetic telescopic tubular mast. This configuration enables synchronized measurement of scalar and vector geomagnetic fields, as well as the attitude, making the payload with its compact sensors suitable for applications on miniature satellite platforms. On November 7, 2022, the novel telescopic tubular mast was deployed in orbit, extending to a length of 5.28 m. The CPTM, an absolute scalar magnetometer with an omnidirectional sensor, is the first China-developed quantum/atomic magnetometer successfully operating in space. In orbit, the CPTM has sensitivity of ⋃10 pT/Hz1/2 and can automatically operate under complex magnetic field variations. The difference between the scalar fields obtained using the CPTM and CHAOS model has a mean deviation of −3.73 nT and a standard deviation of 26.11 nT (1σ), without on-orbit calibration or correction. The miniaturized AMRM has a sensitivity of ⋃0.3 nT/Hz1/2 and maintains stable and reliable operation in orbit. The low-power and miniaturized nano star tracker has a measurement uncertainty of 14.23″ (1σ) in orbit. The mission has realized the on-orbit technical verification of the integrated and synchronized detection of the vector magnetic field and attitude and fully validated the system’s performance, automation level, and reliability.

The search coil magnetometer is widely used in space exploration and geological prospect-ing due to its high sensitivity and low noise level.This study presents a search coil sensor based on a transimpedance preamplifier to achieve a wide frequency bandwidth.The sensor directly connects the output signal of the inductive coil to the transimpedance preamplifier,which converts the AC magnetic field signal into an electrical signal.A signal transfer model of a magnetic sensor based on a tran-simpedance preamplifier is established,and the theoretical formula for sensitivity and noise is deduced.The search coil sensor is designed and developed using this formula to achieve a bandwidth of 0.01～10 kHz and a noise level of 1 fT·Hz-1/2 at 1～10 kHz.A signal modulation method evaluates the sensor's performance for efficient amplitude and phase extraction at a specific frequency.The dual sensor differ-ential method eliminates environmental interference during sensor noise assessment,and a phase differ-ence analysis evaluates the homologous frequency bands of signals detected by two probes.As a result,the sensor achieves a 1 fT·Hz-1/2 noise level in the 1 kHz to 10 kHz range.

Abstract Broadband ELF electrostatic emissions have been observed by the China Seismo‐Electromagnetic Satellite (CSES) inside the equatorial plasma bubbles (EPBs). Analyses reveal that the electric field fluctuates nearly perpendicular to the ambient magnetic field, with the transverse component gyrotropically distributed around the magnetic field line. The observed emissions, Doppler shifted and broadened, are found to be close to the local oxygen ion (O+) cyclotron frequency in the plasma reference frame. Accompanying ion heating and deceleration are consistent with the consequences of the ion cyclotron resonance. All these results indicate that the electrostatic emissions pervading a major part of the EPB are the O+ electrostatic ion cyclotron (EIC) waves. The inhomogeneous‐energy‐density‐driven instability triggered by the non‐uniform electric field and density gradient across the EPBs could be the source of the EIC waves. The CSES observation provides new evidence for the shear driven EIC wave in the equatorial ionosphere.

With the accumulation of data, it is possible to study the long-term variation of Fluxgate Magnetometers (FGM) of High Precision Magnetometer (HPM) onboard the China Seismo-Electromagnetic Satellite (CSES). The calibration method of HPM depends on an assumption that the linear parameters of FGM, including the gain factors, the offsets, and nonorthogonal angles are stable. However, HPM exhibits some unexpected trends in the scalar residuals when processed according to the assumption. Study on the residual finds out that under changing space thermal conditions, the non-orthogonal angles of FGM change periodically, suggesting that the data calibration method we used before should be modified. A multi-dimensional polynomial model is established for defining the change of nonorthogonal angles of FGM as a function of the sun incidence angles, geographic latitude and sensor temperature. Apply the polynomial model to data from August 2018 to May 2021, the standard deviation of the scalar residuals is reduced to around 0.5 nT and tends to be more random and in line with the normal distribution. Meanwhile, the variation trend in gain factors and offset factors are eliminated. Results show that the model can correctly reflect the period variation of the non-orthogonal angles of FGM with the space thermal conditions.

Based on the in-orbit magnetic field data of the China Seismo-Electromagnetic Satellite (CSES) and Swarm satellites, some research studies on the data consistency cross comparison were carried out. The condition applied is that two satellites pass by in a relatively short period of time and through the spatial location at a relatively close range, and different spatial-temporal scale standards were set, combined with the Kp index to screen for geomagnetic quiet periods. Then, with the help of the CHAOS model, indirect analysis was realized. Furthermore, the difference between the in-orbit data and model value was visualized, and the phenomenon and possible reason for data variation with time and geomagnetic latitude variation were analyzed. These analysis results are displayed in this study, which may evaluate the reliability of the satellite magnetic field detection data and the consistency of multiple satellite detection results and provide a methodological reference for carrying out similar evaluation and analysis subsequently.

This paper describes the development of the fluxgate magnetometer on the Fengyun-4B satellite. The Fengyun-4 is the second generation of China’s geostationary orbit satellite with the function of monitoring the space environment in GEO orbit. A fluxgate magnetometer (FGM) is deployed on this satellite to observe the magnetic field as a necessary input to space weather forecasting. This payload adopts three 3-axis fluxgate sensors to obtain space magnetic field data by excluding the satellite’s interference. Each three-axis fluxgate sensor has an independent signal processing circuit. FGM uses digital signal processing technology to acquire magnetic field signals. First, the analog signal is oversampled using a high-speed ADC, then digital signal processing, such as phase-sensitive demodulation, integration, and filtering, is performed inside the FPGA, and the feedback signal is output to the feedback coil through the DAC. This signal processing loop constitutes an ADC system, and the quantization accuracy of the output digital quantity can reach 18 bits. the FGM performs in-orbit calibration during satellite rotation maneuver and Alfven wave events. Comparison with the GOES-16 satellite and Tsyganenko magnetic field model proves FGM to be effective in monitoring the magnetic field of the space environment. Through joint observations with GOES-16 satellite and geomagnetic stations, FY-4B describes the development of a typical magnetic storm on November 4, 2021. The Ground calibration and in-orbit preliminary results show the FY-4B satellite magnetometer outputs 20 bits of digital resolution data at a 30 Hz sampling rate, with the noise lower than 3×10-4nT2/Hz@1Hz in the ±600nT range.

High precision magnetometer (HPM) is a magnetic field detection payload onboard China Seismo-Electromagnetic Satellite (CSES), including two fluxgate magnetometers (FGM) and a coupled dark state magnetometer (CDSM). Observations show that FGM appears to be influenced when tri-band beacon (TBB) is powered on and emits electromagnetic waves. The interference phenomenon is further validated based on both in-orbit observation analysis and electromagnetic compatibility (EMC) tests on the ground. A joint correction algorithm based on the least square fitting and first-order difference method according to scalar magnetometer data is proposed to eliminate the interference. The algorithm significantly improves the consistency of HPM data. After correction, the average scalar deviation error could be reduced from 9.0 nT to around 0.7 nT.

Processes and threats related to natural hazards play an important role in the evolution of the Earth and in human history. The purpose of this study is to investigate magnetic field variations measured at low Earth orbit (LEO) altitudes possibly associated with earthquakes, volcanic eruptions, and artificial outbursts. We focus on two missions with well equipped magnetometer packages, the China Seismo-Electromagnetic Satellite (CSES) and ESA's three spacecraft Swarm fleet. After a natural hazards survey in the context of this satellites, and consideration of external magnetospheric and solar influences, together with spacecraft interferences, wavelet analysed spatio-temporal patterns in ionospheric magnetic field variations related to atmospheric waves are examined in detail. We provide assessment of the links between specific lithospheric or near surface sources and ionospheric magnetic field measurements. For some of the diverse events the achieved statistical results show a change in the pattern between pre- and post-event periods, we show there is an increase in the fluctuations for the higher frequency (smaller scales) components. Our results are relevant to studies which establish a link between space based magnetic field measurements and natural hazards.

Using magnetic field data from the China Seismo-Electromagnetic Satellite (CSES) mission, we derive a global geomagnetic field model, which we call the CSES Global Geomagnetic Field Model (CGGM). This model describes the Earth’s magnetic main field and its linear temporal evolution over the time period between March 2018 and September 2019. As the CSES mission was not originally designed for main field modelling, we carefully assess the ability of the CSES orbits and data to provide relevant data for such a purpose. A number of issues are identified, and an appropriate modelling approach is found to mitigate these. The resulting CGGM model appears to be of high enough quality, and it is next used as a parent model to produce a main field model extrapolated to epoch 2020.0, which was eventually submitted on October 1, 2019 as one of the IGRF-13 2020 candidate models. This CGGM candidate model, the first ever produced by a Chinese-led team, is also the only one relying on a data set completely independent from that used by all other candidate models. A successful validation of this candidate model is performed by comparison with the final (now published) IGRF-13 2020 model and all other candidate models. Comparisons of the secular variation predicted by the CGGM parent model with the final IGRF-13 2020–2025 predictive secular variation also reveal a remarkable agreement. This shows that, despite their current limitations, CSES magnetic data can already be used to produce useful IGRF 2020 and 2020–2025 secular variation candidate models to contribute to the official IGRF-13 2020 and predictive secular variation models for the coming 2020–2025 time period. These very encouraging results show that additional efforts to improve the CSES magnetic data quality could make these data very useful for long-term monitoring of the main field and possibly other magnetic field sources, in complement to the data provided by missions such as the ESA Swarm mission.

Providing accurate measurement of the magnetic field intensity and its vector components is one of the primary objectives of the China Seismo‐Electromagnetic Satellite (CSES). The high precision magnetometer (HPM) payload assembled on CSES is designed to achieve this goal. In this study, the data format, naming convention, and content of the CSES HPM Level 2 scientific data products are introduced, as a reference for users who are interested in this data set. In particular, flags for potential magnetic field disturbances from the platform and payloads are discussed. Possible scientific applications are also outlined. A preliminary validation of the data is conducted through comparison with magnetic data from the ESA’s Swarm constellation, and the result demonstrates that the HPM data of CSES are of good quality. Taking the intense geomagnetic storm that occurred on August 25–26, 2018 as an example, the magnetic field variations and the expansion of the field‐aligned currents (FACs) during this storm are discussed. We finally show that the CSES HPM data can be used to derive a satellite‐derived index equivalent to the Dst index, which agrees well to the index during this event. Our analysis thus suggests a high scientific potential of the HPM data.

With a new type of a scalar magnetometer, the Coupled Dark State Magnetometer (CDSM) aboard the China Seismo-Electromagnetic Satellite (CSES) mission, we observed magnetic field fluctuations in the period mid July 2018 until mid November 2018. The measurement range of the CDSM is from 1000 nT up to 100000 nT and the accuracy 0.19 nT (1), the operational performance is discussed in (2). We are using 1 Hz data in the latitude range -65 degree to +65 degree, CSES has an altitude of approx. 507 km in Sun synchronous polar configuration with 97.4 degree inclination. We analyzed the total magnetic field turbulence by converting the time series into thermodynamic parameters, e.g. entropy, finally these results have been compared with ground based seismic and volcanic events. Ref: (1) Pollinger, A., et al.: Coupled dark state magnetometer for the China Seismo-Electromagnetic Satellite, Measurement Science and Technology, 29, 9, 2018. https://doi.org/10.1088/1361-6501/aacde4 (2) Pollinger, A., et al.: In-orbit results of the Coupled Dark State Magnetometer aboard the China Seismo-Electromagnetic Satellite, Geosci. Instrum. Method. Data Syst., 9, 275–291, 2020. https://doi.org/10.5194/gi-9-275-2020

Abstract. During the storm recovery phase on August 27, 2018, the China Seismo-Electromagnetic Satellite (CSES) detected Pc1 wave activities both in the Northern and Southern hemispheres in the high latitude post-midnight ionosphere with a central frequency about 2 Hz. Meanwhile, the typical Pc1 waves were simultaneously observed by the Sodankylä Geophysical Observatory (SGO) stations on the ground for several hours. In this paper, we study the propagation characteristics and possible source regions of those waves. Firstly, we find that the satellites observed Pc1 waves exhibit mixed polarization and the wave normal is almost parallel with the background magnetic field. The field-aligned Poynting fluxes point downward in both hemispheres, implying the satellites are close to the wave injection regions in the ionosphere at about L = 3. Furthermore, we also find that the estimated position of the plasmapause calculated by models is almost at L = 3. Therefore, we suggest the possible sources of waves are near the plasmapause, which is consistent with previous studies that the outward expansion of the plasmasphere into the ring current during the recovery phase of geomagnetic storms may generate electromagnetic ion cyclotron (EMIC) waves and then these EMIC waves propagate along the background magnetic field northward and southward to the ionosphere at about L = 3. Additionally, the ground station data show that Pc1 wave power attenuates with increasing distance from L = 3, supporting the idea that CSES observes the wave activities near the injection region. The observations are unique in that the Pc1 waves are observed in the ionosphere in nearly conjugate regions, where transvers Alfven waves propagate down into the ionosphere.

11 During the storm recovery phase on August 27, 2018, the China Seismo12 Electromagnetic Satellite (CSES) detected Pc1 wave activities both in the Northern and 13 Southern hemispheres in the high latitude post-midnight ionosphere with a central 14 frequency about 2 Hz. Meanwhile, the typical Pc1 waves were simultaneously 15 observed by the Sodankylä Geophysical Observatory (SGO) stations on the ground for 16 several hours. In this paper, we study the propagation characteristics and possible 17 source regions of those waves. Firstly, we find that the Pc1 waves observed by the 18 satellites exhibited mixed polarization and the wave normal is almost parallel with the 19 background magnetic field. The field-aligned Poynting fluxes point downward in both 20 hemispheres, implying the satellites are close to the wave injection regions in the 21 ionosphere at about L=3. Furthermore, we also find that the estimated position of the 22 plasmapause calculated by models is almost at L=3. Therefore, we suggest the possible 23 sources of waves are near the plasmapause, which is consistent with previous studies 24 that the outward expansion of the plasmasphere into the ring current during the 25 recovery phase of geomagnetic storms may generate electromagnetic ion cyclotron 26 (EMIC) waves and then these EMIC waves propagate along the background magnetic 27 field northward and southward to the ionosphere at about L=3. Additionally, the 28 ground station data show that Pc1 wave power attenuates with increasing distance 29 from L=3, supporting the idea that CSES observes the wave activities near the injection 30 region. The observations are unique in that the Pc1 waves are observed in the 31 ionosphere in nearly conjugate regions, where transvers Alfven waves propagate down 32 into the ionosphere. 33