The Low Earth Orbit(LEO)geomagnetic satellites provide a large number of high-precision measurements,which are crucial for researching the Secular Variation(SV)of the geomagnetic field.We employ the combined constella...The Low Earth Orbit(LEO)geomagnetic satellites provide a large number of high-precision measurements,which are crucial for researching the Secular Variation(SV)of the geomagnetic field.We employ the combined constellation data from the Chinese Seismo-Electromagnet Satellite(CSES)and Swarm satellites to extract the SV in China and surrounding areas,based on the Geomagnetic Virtual Observatory(GVO)method.On this basis,we have developed two GVO products:the core field,and the SV series.The accuracies of these products are assessed using ground observatories measurements and geomagnetic field model.Moreover,the results indicate that the GVO products align well with the series from ground observatories and the CHAOS model.The majority of root-mean-square deviation(RMSE)values of the core field series are less than 5 nT,consistent with the INTERMAGNET standards for quasi-definitive data.In the GVO core field series,the maximum accuracy of one-month and four-month intervals are 2.24 nT and 1.16 nT,respectively.In the GVO SV series,the maximum accuracy of one-month and four-month intervals are 2.03 nT/yr and 1.36 nT/yr,respectively.The GVO SV series effectively capture geomagnetic jerks without losing temporal resolution comparing with the recording of ground observatories.We demonstrate that the GVO method serves as an effective and precise tool for extracting SV information of geomagnetic fields.In the GVO products,the RMSE of the horizontal component exceeds that of the vertical component,and the magnitude of RMSE deviation correlates with solar activity levels.With more and more geomagnetic satellites in orbit,we wish to use multi-constellation magnetic satellite data to assess the geomagnetic field more accurately.展开更多
Earth’s internal core and crustal magnetic fields,as measured by geomagnetic satellites like MSS-1(Macao Science Satellite-1)and Swarm,are vital for understanding core dynamics and tectonic evolution.To model these i...Earth’s internal core and crustal magnetic fields,as measured by geomagnetic satellites like MSS-1(Macao Science Satellite-1)and Swarm,are vital for understanding core dynamics and tectonic evolution.To model these internal magnetic fields accurately,data selection based on specific criteria is often employed to minimize the influence of rapidly changing current systems in the ionosphere and magnetosphere.However,the quantitative impact of various data selection criteria on internal geomagnetic field modeling is not well understood.This study aims to address this issue and provide a reference for constructing and applying geomagnetic field models.First,we collect the latest MSS-1 and Swarm satellite magnetic data and summarize widely used data selection criteria in geomagnetic field modeling.Second,we briefly describe the method to co-estimate the core,crustal,and large-scale magnetospheric fields using satellite magnetic data.Finally,we conduct a series of field modeling experiments with different data selection criteria to quantitatively estimate their influence.Our numerical experiments confirm that without selecting data from dark regions and geomagnetically quiet times,the resulting internal field differences at the Earth’s surface can range from tens to hundreds of nanotesla(nT).Additionally,we find that the uncertainties introduced into field models by different data selection criteria are significantly larger than the measurement accuracy of modern geomagnetic satellites.These uncertainties should be considered when utilizing constructed magnetic field models for scientific research and applications.展开更多
The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic...The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic field has not been previously estimated or incorporated into geomagnetic field models,potentially causing leakage into the core field model.Here,we present a method to account for the circulation-induced magnetic field during geomagnetic field modeling.First,a forward model of the circulation-induced magnetic field is constructed by numerically solving electromagnetic induction equations based on a realistic ocean circulation model.Then,this forward model is subtracted from the observed data.Finally,the core and lithospheric fields,magnetospheric and Earth’s mantle-induced fields,and the ocean tide-induced magnetic field are co-estimated.Applying our method to over 20 years of MSS-1,Swarm,CryoSat-2,and CHAMP satellite magnetic data,we derive a new multisource geomagnetic field model(MGFM).We find that incorporating a forward model of the circulation-induced magnetic field marginally improves the fit to the data.Furthermore,we demonstrate that neglecting the circulation-induced magnetic field in geomagnetic field modeling results in leakage into the core field model.The highlights of the MGFM model include:(i)a good agreement with the widely used CHAOS model series;(ii)the incorporation of magnetic fields induced by both ocean tides and circulation;and(iii)the suppression of leakage of the circulation-induced magnetic field into the core field model.展开更多
Measurements from geomagnetic satellites continue to underpin advances in geomagnetic field models that describe Earth's internally generated magnetic field.Here,we present a new field model,MSCM,that integrates v...Measurements from geomagnetic satellites continue to underpin advances in geomagnetic field models that describe Earth's internally generated magnetic field.Here,we present a new field model,MSCM,that integrates vector and scalar data from the Swarm,China Seismo-Electromagnetic Satellite(CSES),and Macao Science Satellite-1(MSS-1)missions.The model spans from 2014.0 to 2024.5,incorporating the core,lithospheric,and magnetospheric fields,and it shows characteristics similar to other published models based on different data.For the first time,we demonstrate that it is possible to successfully construct a geomagnetic field model that incorporates CSES vector data,albeit one in which the radial and azimuthal CSES vector components are Huber downweighted.We further show that data from the MSS-1 can be integrated within an explicitly smoothed,fully time-dependent model description.Using the MSCM,we identify new behavior of the South Atlantic Anomaly,the broad region of low magnetic field intensity over the southern Atlantic.This prominent feature appears split into a western part and an eastern part,each with its own intensity minimum.Since 2015,the principal western minimum has undergone only modest intensity decreases of 290 nT and westward motion of 20 km per year,whereas the recently formed eastern minimum has shown a 2–3 times greater intensity drop of 730 nT with no apparent east-west motion.展开更多
Geomagnetic observatory data are crucial for all branches of geophysics because they can contribute to earthquake research by detecting anomalies in the Earth’s magnetic field.Recently,data records from the Misallat(...Geomagnetic observatory data are crucial for all branches of geophysics because they can contribute to earthquake research by detecting anomalies in the Earth’s magnetic field.Recently,data records from the Misallat(MLT)and Abu Simbel(ABS)Egyptian geomagnetic observatories were processed and found to be of good quality.In this study,Egyptian observatory data were tested during both quiet and disturbed events and compared with data from INTERMAGNET observatories worldwide at different latitudes and within a narrow range of longitudes in both hemispheres.This study investigated the relationships between magnetic field components from Egyptian observatories and those from INTERMAGNET observatories using graphical representations of the X components;Pearson’s correlation for the X,Y,Z,and F components;cross-correlation for the X component;and wavelet coherence for the F component.The results of this study showed a high correlation between Egyptian observatories and all utilized INTERMAGNET stations,except those located at high latitudes,during both quiet and disturbed events.Additionally,the study confirmed the observed consistency between Egyptian observatories and selected INTERMAGNET stations.Therefore,Egyptian observatories can feasibly fill the gap in the Middle East and North Africa.展开更多
This study utilizes radio occultation observations from the Macao Science Satellite-1 mission(MSS-1)to investigate ionospheric response to the May 2024 G5 geomagnetic storm within the South Atlantic Anomaly(SAA)region...This study utilizes radio occultation observations from the Macao Science Satellite-1 mission(MSS-1)to investigate ionospheric response to the May 2024 G5 geomagnetic storm within the South Atlantic Anomaly(SAA)region.The distinctive data from MSS-1,complemented by observations from the ground-based Global Navigation Satellite System(GNSS)and the Constellation Observing System for Meteorology,Ionosphere,and Climate follow-on satellite mission(COSMIC-2),reveal a super plasma fountain effect during the main phase of the storm.This effect was marked by peaks in the equatorial ionization anomaly that extended beyond their typical latitude range.The MSS-1 observations,particularly in the northern hemisphere of the SAA region,confirm the role of prompt penetration electric fields in driving ionospheric disturbances and amplifying scintillation at higher altitudes.The study also identifies a decrease in total electron content and a reduction in scintillation occurrence during the recovery phase of the storm.The results demonstrate the pivotal role that MSS-1 observations can play,when combined with ground-based and COSMIC-2 observations,in providing a more comprehensive understanding of ionospheric response to severe geomagnetic storms.展开更多
The Sq(solar quiet)geomagnetic field is generated by the electric currents in the E-region of the ionosphere,driven by the atmospheric tides.It is a critical part of high-precision geomagnetic field modeling.Based on ...The Sq(solar quiet)geomagnetic field is generated by the electric currents in the E-region of the ionosphere,driven by the atmospheric tides.It is a critical part of high-precision geomagnetic field modeling.Based on the classic thermal tide theory and atmospheric electrodynamics,this research,for the first time,developed an Sq geomagnetic field model that is directly built on the physical mechanism of the ionospheric dynamo,which is responsible for daily variations of the geomagnetic field.The performance in Sq geomagnetic field modeling was investigated using the Macao Science Satellite-1(MSS-1)data.Our model can enhance the physics-based framework of comprehensive geomagnetic field modeling for the MSS-1 and ensuing missions.展开更多
Strong flares and/or coronal mass ejections(CMEs) could bring us disastrous space weather,destroy crucial technology in space,and cause a large-scale blackout during some extreme cases.They frequently cause geomagneti...Strong flares and/or coronal mass ejections(CMEs) could bring us disastrous space weather,destroy crucial technology in space,and cause a large-scale blackout during some extreme cases.They frequently cause geomagnetic storms,which is a sudden disturbance of the Earth's magnetosphere.It is well accepted that CMEs play a dominant role in causing geomagnetic storms by a direct impact,but it is still not very clear regarding their association with solar flares.The association would be helpful for forecasting geomagnetic storms directly from flares,which are much easier to observe.The Macao Science Satellite-1(MSS-1) mission,with the scientific aim of studying the origin and evolution of the geomagnetic field,is able to accurately measure the vector geomagnetic field.Besides,it measures rapid spectral evolution of the solar X-ray irradiance of solar flares.In this study,we analyzed measurements by MSS-1 during a series of X-class flares in October of 2024,and saw the relationship between the flares and the associated geomagnetic storms.The observations support that the major geomagnetic storms tend to be associated with flares' duration in addition to flare class.We also find that long duration ones have radiated more energy in the extreme ultraviolet waveband.Being equally important,our results show that the magnetic fields measured by MSS-1,especially its external(e_(1)^(0)) coefficient,can well be used for monitoring the geomagnetic disturbance.展开更多
The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospher...The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations.展开更多
Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked t...Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked to equatorial plasma bubbles(EPBs),regions of depleted plasma density that form after sunset.Ionospheric scintillation typically occurs from post-sunset hours until midnight.Post-sunset EPBs can be enhanced or suppressed during geomagnetic storms,depending on local sunset timing and how it relates to the storm's main or recovery phases.This study analyzes ionospheric scintillation in Indonesia,located at low geomagnetic and geographic latitudes,during geomagnetic events from 2003 to 2024.Using the S4 index,scintillation was examined with data from seven observation stations during geomagnetic storm events.Geomagnetic activity was evaluated using Dst,SYM-H,and AE indices,employing Superposed Epoch Analysis(SEA)to assess scintillation occurrence linked to minimum SYM-H,defined as epoch 0 to represent the storm peak or the onset of recovery phase in each event.The analysis categorized geomagnetic storms into weak-moderate(–100 nT<min.Dst≤–30 nT)and strong(min.Dst≤–100 nT),and examined their dependence on the local time of minimum SYM-H.Results indicate that scintillation first appears~6 hours after epoch 0 in weak-moderate geomagnetic storms,and~12 hours after epoch 0 in strong geomagnetic storms.The average AE index returns to its baseline value(quiet condition)~6 and~12 hours after epoch 0 for weak-moderate and strong geomagnetic storms,respectively.Further analysis based on the classification of the local time of epoch 0 shows that scintillation occurrence is not observed in post-sunset hours when epoch 0 falls between 16:00 and 19:00 LT for weak-moderate geomagnetic storms.In strong geomagnetic storms,scintillation occurrence during post-sunset hours is absent when epoch 0 is between 10:00 and 19:00 LT.Notably,when the minimum SYM-H(epoch 0)nearly coincides with local sunset,scintillation activity occurs around sunset in both weak-moderate and strong geomagnetic storms.Furthermore,when epoch 0 falls within midnight until early morning,scintillation can be generated in the post-sunset hours before epoch 0.Still,post-midnight scintillation is not observed in the equatorial region during the recovery phase of either weak-moderate and strong storm events.Our findings show that when sunset falls before or coincide with epoch 0,the likelihood of post-sunset EPB and scintillation increases,due to the prompt-penetration electric field(PPEF)in the main phase of storm.The disturbance dynamo electric field(DDEF)in the recovery phase driven by equatorward winds from auroral Joule heating operates for at least 6-and 12-hours post-epoch 0 in the cases of weak-moderate and strong geomagnetic storms,respectively.When the local sunset falls within these operational DDEF periods,post-sunset EPBs will likely be suppressed,inhibiting ionospheric scintillation during post-sunset hours.Finally,this study provides essential information for developing more accurate ionospheric scintillation prediction models in space weather services in equatorial regions.展开更多
This study systematically analyzed the spatiotemporal evolution characteristics of geomagnetic anomalies before and after the 2013 Sichuan Lushan M7.0 earthquake and the Gansu Minxian M6.6 earthquake by constructing a...This study systematically analyzed the spatiotemporal evolution characteristics of geomagnetic anomalies before and after the 2013 Sichuan Lushan M7.0 earthquake and the Gansu Minxian M6.6 earthquake by constructing a geomagnetic diurnal variation model based on Taylor polynomial fitting,combined with midnight mean values of the geomagnetic F component from China,s geomagnetic observatory network.The results reveal distinct differences in anomaly patterns,namely per-sistent positive anomalies were observed in the epicentral region of the Lushan earthquake,while significant negative anomalies characterized the Minxian earthquake zone.This differential response reveals the modulating effect of the electrical structure of the seismogenic medium on space electromagnetic disturbances,namely positive anomalies may correspond to the stage of stable stress accumulation in intact rock,while the expansion of negative anomalies may reflect an amplification of electromagnetic disturbances induced by fracture expansion.Further analysis demonstrates that both anomalies exhibit a three-stage evolutionary pattern,namely pre-seismic accumulation,co-seismic release,and post-seismic adjustment.The phase transitions in these anomalies are closely correlated with regional tectonic stress accumulation and destabilization processes.These findings not only provide new evidence for the physical interpretation of seismomagnetic precursors but also establish a theoretical foundation for developing earthquake prediction methods based on the dynamic evolution of geomagnetic anomalies.展开更多
Proper knowledge of the nature of geomagnetic storms and their relationships with the conditions of the space environment at the outer part of the Earth's magnetosphere(bow shock nose) is essential to increase our...Proper knowledge of the nature of geomagnetic storms and their relationships with the conditions of the space environment at the outer part of the Earth's magnetosphere(bow shock nose) is essential to increase our resilience to space weather disturbances. In this article, we present an analysis of the interplanetary magnetic field(IMF) and solar wind parameters relevant to 100 geomagnetic storms in Solar Cycle 24. We revisit the relationship between the minimum disturbance storm time index(Dst_(min)), the minimum southward IMF(B_(S, min)), the maximum solar wind density(N_(SW, max)) and speed(V_(max)), and the lag time between the extrema(dT(B_(z), N),dT(B_(z), V)). We end with a regression formula that fits the data, with a coefficient of determination of 0.58, a root mean square error of 21.30 nT, and a mean absolute error of 15.87 nT. Even though more complex machine learning models can outperform this model, it serves as a theoretically sensible alternative for understanding and forecasting geomagnetic storms.展开更多
Geomagnetic data hold significant value in fields such as earthquake monitoring and deep earth exploration.However,the increasing severity of anthropogenic noise contamination in existing geomagnetic observatory data ...Geomagnetic data hold significant value in fields such as earthquake monitoring and deep earth exploration.However,the increasing severity of anthropogenic noise contamination in existing geomagnetic observatory data poses substantial challenges to high-precision computational analysis of geomagnetic data.To overcome this problem,we propose a denoising method for geomagnetic data based on the Residual Shrinkage Network(RSN).We construct a sample library of simulated and measured geomagnetic data develop and train the RSN denoising network.Through its unique soft thresholding module,RSN adaptively learns and removes noise from the data,effectively improving data quality.In experiments with noise-added measured data,RSN enhances the quality of the noisy data by approximately 12 dB on average.The proposed method is further validated through denoising analysis on measured data by comparing results of time-domain sequences,multiple square coherence and geomagnetic transfer functions.展开更多
Modeling and forecasting of the geomagnetic variation are important research topics concerning geomagnetic navigation and space environment monitoring.We propose a combined forecasting model using a dynamic recursive ...Modeling and forecasting of the geomagnetic variation are important research topics concerning geomagnetic navigation and space environment monitoring.We propose a combined forecasting model using a dynamic recursive neural network called echo state network(ESN),the method of complementary ensemble empirical mode decomposition(EEMD)and the complexity theory of sample entropy(SampEn).Firstly,we use EEMD-SampEn to decompose the geomagnetic variation time series into many series of geomagnetic variation subsequences whose complexity degrees are transparently different.Then,we use ESN to build a forecasting model for each subsequence,selecting the optimal model parameters.Finally,we use the real data collected from the geomagnetic observatory to conduct simulations.The results show that the forecasting value of the combined model can closely conform to the tendency of geomagnetic variation field,and is superior to the least square support vector machine(LSSVM)model.The mean absolute error of the model for three-hour forecasting is less than 1.40nT when Kp index is less than 3.展开更多
Vector magnetic measurement is increasingly widely used.In order to improve the accuracy of vector magnetic measurement system on board a vehicle,researchers have proposed various calibration methods.Most of them requ...Vector magnetic measurement is increasingly widely used.In order to improve the accuracy of vector magnetic measurement system on board a vehicle,researchers have proposed various calibration methods.Most of them require altering the magnetic vector in the vehicle coordinate system.Exploring the use of geomagnetic variation to change the geomagnetic vector in the vehicle coordinate system,this paper proposes a novel vector magnetic measurement calibration method.In this method,a vector magnetometer mounted on a vehicle and an accurate vector magnetometer separately measure the geomagnetic field at diff erent locations within the same area.Based on the physical principle that the geomagnetic variation at two nearby locations is equal,the calibration parameters of the magnetometer on the vehicle can be determined through a set of equations containing the measurements from the two magnetometers.The theoretical derivation and simulation experiment results demonstrate the feasibility of this method.Therefore,it can serve as a new alternative calibration method,especially in scenarios where a high degree of accuracy in the estimation of calibration parameters is not required.展开更多
Accurately predicting geomagnetic field is of great significance for space environment monitoring and space weather forecasting worldwide.This paper proposes a vision Transformer(ViT)hybrid model that leverages aurora...Accurately predicting geomagnetic field is of great significance for space environment monitoring and space weather forecasting worldwide.This paper proposes a vision Transformer(ViT)hybrid model that leverages aurora images to predict local geomagnetic station component,breaking the spatial limitations of geomagnetic stations.Our method utilizes the ViT backbone model in combination with convolutional networks to capture both the large-scale spatial correlation and distinct local feature correlation between aurora images and geomagnetic station data.Essentially,the model comprises a visual geometry group(VGG)image feature extraction network,a ViT-based encoder network,and a regression prediction network.Our experimental findings indicate that global features of aurora images play a more substantial role in predicting geomagnetic data than local features.Specifically,the hybrid model achieves a 39.1%reduction in root mean square error compared to the VGG model,a 29.5%reduction compared to the ViT model and a 35.3%reduction relative to the residual network(ResNet)model.Moreover,the fitting accuracy of the model surpasses that of the VGG,ViT,and ResNet models by 2.14%1.58%,and 4.1%,respectively.展开更多
Based on the existing geomagnetic diurnal variation theory and correction method,this paper makes a comprehensive analysis of the international geomagnetic quiet diurnal variation by Fourier Transform and one-dimensio...Based on the existing geomagnetic diurnal variation theory and correction method,this paper makes a comprehensive analysis of the international geomagnetic quiet diurnal variation by Fourier Transform and one-dimensional Continuous Wavelet Transform.The frequency band greater than 0.2 Hz is the embodiment of the geomagnetic disturbance field in the frequency domain.Discrete Wavelet Transform is used to separate the variation,thus improving accuracy of the existing geomagnetic diurnal variation correction method.According to the characteristics of variation and Discrete Wavelet Decomposition,Sym8 wavelet is selected as the basic wavelet to decompose the data at 7 layers.The long-term and short-term variation of geomagnetic diurnal variation are effectively separated from the geomagnetic disturbance part under the condition of ensuring the fidelity.Compared with the results of Fourier Series decomposition and low-pass filter,the processing effect of Discrete Wavelet Transform is better.The effective separation and correction of short-term,long-term variation and geomagnetic disturbances can improve the quality of diurnal variation correction in marine geomagnetic measurement,reduce the error accumulation in the process of marine geomagnetic data processing,and improve the scientificity and accuracy of the current diurnal variation correction methods.展开更多
In this paper,we simulate,verify,and compare the performance of three classical geomagnetic matching aided navigation algorithms to assess their applicability to hypersonic vehicle navigation.Firstly,we introduce the ...In this paper,we simulate,verify,and compare the performance of three classical geomagnetic matching aided navigation algorithms to assess their applicability to hypersonic vehicle navigation.Firstly,we introduce the various sources of the geomagnetic field.Secondly,we describe the principles and processes of the geomagnetic contour matching(MAGCOM)algorithm,iterative closest contour point(ICCP)algorithm,and Sandia inertial magnetic aided navigation(SIMAN)algorithm.Thirdly,we discuss the principles of inertial/geomagnetic integrated navigation,and propose the state and observation equations of integrated navigation.Finally,we perform a simulation of inertial/geomagnetic integrated navigation on the hypersonic boost-glide vehicle trajectory.The simulation results indicate that the real-time performance of the SIMAN algorithm can be optimized such that the matching accuracy is higher than that of the other two algorithms.At the same time,the SIMAN algorithm can achieve better stability,and though the amount of measurement noise can be larger,it can still achieve good positioning accuracy.展开更多
Owing to the lack of information about geomagnetic anomaly fields,conventional geomagnetic matching algorithms in near space are prone to divergence.Therefore,geomagnetic matching navigation algorithms for hypersonic ...Owing to the lack of information about geomagnetic anomaly fields,conventional geomagnetic matching algorithms in near space are prone to divergence.Therefore,geomagnetic matching navigation algorithms for hypersonic vehicles are also prone to divergence or mismatch.To address this problem,we propose a multi-geomagnetic-component assisted localization(MCAL)algorithm to improve positioning accuracy using only the information of the main geomagnetic field.First,the main components of the geomagnetic field and a mathematical representation of the Earth’s geomagnetic field(World Magnetic Model 2015)are introduced.The mathematical relationships between the geomagnetic components are given,and the source of geomagnetic matching error is explained.We then propose the MCAL algorithm.The algorithm uses the intersections of the isopleths of the geomagnetic components and a decision method to estimate the real position of a carrier with high positioning accuracy.Finally,inertial/geomagnetic integrated navigation is simulated for hypersonic boost-glide vehicles.The simulation results demonstrate that the proposed algorithm can provide higher positioning accuracy than conventional geomagnetic matching algorithms.When the random error range is±30 nT,the average absolute latitude error and longitude error of the MCAL algorithm are 151 m and 511 m lower,respectively,than those of the Sandia inertial magnetic aided navigation(SIMAN)algorithm.展开更多
By calculating the hourly standard deviation of the first-order differences of the horizontal geomagnetic com- ponent minute data, a new index Vr to represent the variation rate of the geomagnetic field was introduced...By calculating the hourly standard deviation of the first-order differences of the horizontal geomagnetic com- ponent minute data, a new index Vr to represent the variation rate of the geomagnetic field was introduced. Vr-indices show similar trends in the temporal change at different observatories and have simultaneous peak values at the observatories cov- ering a large span geographically, which reveals that the source of geomagnetic disturbances represented by Vr is in the mag- netosphere. Based on the comparison among Vr, Kp and ap, it is found that generally Vr changes linearly with Kp and ap, which means that the rapid changes of magnetic field usually exist together with magnetic disturbances. But there are excep- tions. As Vr can be easily produced by individual observatory in quasi real time and is more sensitive to the variation rate of geomagnetic field rather than the field itself, it can be expected to serve for monitoring or predicting the geomagnetic-induced event in a quick and intuitive way.展开更多
基金supported by the Special Fund of the Institute of Geophysics,China Earthquake Administration(grant no.DQJB24X25).
文摘The Low Earth Orbit(LEO)geomagnetic satellites provide a large number of high-precision measurements,which are crucial for researching the Secular Variation(SV)of the geomagnetic field.We employ the combined constellation data from the Chinese Seismo-Electromagnet Satellite(CSES)and Swarm satellites to extract the SV in China and surrounding areas,based on the Geomagnetic Virtual Observatory(GVO)method.On this basis,we have developed two GVO products:the core field,and the SV series.The accuracies of these products are assessed using ground observatories measurements and geomagnetic field model.Moreover,the results indicate that the GVO products align well with the series from ground observatories and the CHAOS model.The majority of root-mean-square deviation(RMSE)values of the core field series are less than 5 nT,consistent with the INTERMAGNET standards for quasi-definitive data.In the GVO core field series,the maximum accuracy of one-month and four-month intervals are 2.24 nT and 1.16 nT,respectively.In the GVO SV series,the maximum accuracy of one-month and four-month intervals are 2.03 nT/yr and 1.36 nT/yr,respectively.The GVO SV series effectively capture geomagnetic jerks without losing temporal resolution comparing with the recording of ground observatories.We demonstrate that the GVO method serves as an effective and precise tool for extracting SV information of geomagnetic fields.In the GVO products,the RMSE of the horizontal component exceeds that of the vertical component,and the magnitude of RMSE deviation correlates with solar activity levels.With more and more geomagnetic satellites in orbit,we wish to use multi-constellation magnetic satellite data to assess the geomagnetic field more accurately.
基金supported by the National Natural Science Foundation of China(42250101)the Macao Foundation。
文摘Earth’s internal core and crustal magnetic fields,as measured by geomagnetic satellites like MSS-1(Macao Science Satellite-1)and Swarm,are vital for understanding core dynamics and tectonic evolution.To model these internal magnetic fields accurately,data selection based on specific criteria is often employed to minimize the influence of rapidly changing current systems in the ionosphere and magnetosphere.However,the quantitative impact of various data selection criteria on internal geomagnetic field modeling is not well understood.This study aims to address this issue and provide a reference for constructing and applying geomagnetic field models.First,we collect the latest MSS-1 and Swarm satellite magnetic data and summarize widely used data selection criteria in geomagnetic field modeling.Second,we briefly describe the method to co-estimate the core,crustal,and large-scale magnetospheric fields using satellite magnetic data.Finally,we conduct a series of field modeling experiments with different data selection criteria to quantitatively estimate their influence.Our numerical experiments confirm that without selecting data from dark regions and geomagnetically quiet times,the resulting internal field differences at the Earth’s surface can range from tens to hundreds of nanotesla(nT).Additionally,we find that the uncertainties introduced into field models by different data selection criteria are significantly larger than the measurement accuracy of modern geomagnetic satellites.These uncertainties should be considered when utilizing constructed magnetic field models for scientific research and applications.
基金supported by the National Natural Science Foundation of China(42250101,42250102)the Macao Foundation.
文摘The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic field has not been previously estimated or incorporated into geomagnetic field models,potentially causing leakage into the core field model.Here,we present a method to account for the circulation-induced magnetic field during geomagnetic field modeling.First,a forward model of the circulation-induced magnetic field is constructed by numerically solving electromagnetic induction equations based on a realistic ocean circulation model.Then,this forward model is subtracted from the observed data.Finally,the core and lithospheric fields,magnetospheric and Earth’s mantle-induced fields,and the ocean tide-induced magnetic field are co-estimated.Applying our method to over 20 years of MSS-1,Swarm,CryoSat-2,and CHAMP satellite magnetic data,we derive a new multisource geomagnetic field model(MGFM).We find that incorporating a forward model of the circulation-induced magnetic field marginally improves the fit to the data.Furthermore,we demonstrate that neglecting the circulation-induced magnetic field in geomagnetic field modeling results in leakage into the core field model.The highlights of the MGFM model include:(i)a good agreement with the widely used CHAOS model series;(ii)the incorporation of magnetic fields induced by both ocean tides and circulation;and(iii)the suppression of leakage of the circulation-induced magnetic field into the core field model.
基金supported by the National Natural Science Foundation of China(Grant No.42274003)PWL was supported by Swarm DISC(Swarm Data,Innovation,and Science Cluster)+2 种基金funded by the European Space Agency(ESAContract No.4000109587)HFR acknowledges funding from the UK Natural Environment Research Council(Grant No.NE/V010867/1)。
文摘Measurements from geomagnetic satellites continue to underpin advances in geomagnetic field models that describe Earth's internally generated magnetic field.Here,we present a new field model,MSCM,that integrates vector and scalar data from the Swarm,China Seismo-Electromagnetic Satellite(CSES),and Macao Science Satellite-1(MSS-1)missions.The model spans from 2014.0 to 2024.5,incorporating the core,lithospheric,and magnetospheric fields,and it shows characteristics similar to other published models based on different data.For the first time,we demonstrate that it is possible to successfully construct a geomagnetic field model that incorporates CSES vector data,albeit one in which the radial and azimuthal CSES vector components are Huber downweighted.We further show that data from the MSS-1 can be integrated within an explicitly smoothed,fully time-dependent model description.Using the MSCM,we identify new behavior of the South Atlantic Anomaly,the broad region of low magnetic field intensity over the southern Atlantic.This prominent feature appears split into a western part and an eastern part,each with its own intensity minimum.Since 2015,the principal western minimum has undergone only modest intensity decreases of 290 nT and westward motion of 20 km per year,whereas the recently formed eastern minimum has shown a 2–3 times greater intensity drop of 730 nT with no apparent east-west motion.
文摘Geomagnetic observatory data are crucial for all branches of geophysics because they can contribute to earthquake research by detecting anomalies in the Earth’s magnetic field.Recently,data records from the Misallat(MLT)and Abu Simbel(ABS)Egyptian geomagnetic observatories were processed and found to be of good quality.In this study,Egyptian observatory data were tested during both quiet and disturbed events and compared with data from INTERMAGNET observatories worldwide at different latitudes and within a narrow range of longitudes in both hemispheres.This study investigated the relationships between magnetic field components from Egyptian observatories and those from INTERMAGNET observatories using graphical representations of the X components;Pearson’s correlation for the X,Y,Z,and F components;cross-correlation for the X component;and wavelet coherence for the F component.The results of this study showed a high correlation between Egyptian observatories and all utilized INTERMAGNET stations,except those located at high latitudes,during both quiet and disturbed events.Additionally,the study confirmed the observed consistency between Egyptian observatories and selected INTERMAGNET stations.Therefore,Egyptian observatories can feasibly fill the gap in the Middle East and North Africa.
基金support from the National Natural Science Foundation of China(No.42274027)the Fundamental Research Funds for the Central Universitiessupported also by the Macao Foundation。
文摘This study utilizes radio occultation observations from the Macao Science Satellite-1 mission(MSS-1)to investigate ionospheric response to the May 2024 G5 geomagnetic storm within the South Atlantic Anomaly(SAA)region.The distinctive data from MSS-1,complemented by observations from the ground-based Global Navigation Satellite System(GNSS)and the Constellation Observing System for Meteorology,Ionosphere,and Climate follow-on satellite mission(COSMIC-2),reveal a super plasma fountain effect during the main phase of the storm.This effect was marked by peaks in the equatorial ionization anomaly that extended beyond their typical latitude range.The MSS-1 observations,particularly in the northern hemisphere of the SAA region,confirm the role of prompt penetration electric fields in driving ionospheric disturbances and amplifying scintillation at higher altitudes.The study also identifies a decrease in total electron content and a reduction in scintillation occurrence during the recovery phase of the storm.The results demonstrate the pivotal role that MSS-1 observations can play,when combined with ground-based and COSMIC-2 observations,in providing a more comprehensive understanding of ionospheric response to severe geomagnetic storms.
基金supported by the National Natural Science Foundation of China(Grant Nos.12250013,12403070,12425306,42250101,12273092)the Macao Foundation,and Shanghai Post-doctoral Excellence Program(Grant No.2023000137)。
文摘The Sq(solar quiet)geomagnetic field is generated by the electric currents in the E-region of the ionosphere,driven by the atmospheric tides.It is a critical part of high-precision geomagnetic field modeling.Based on the classic thermal tide theory and atmospheric electrodynamics,this research,for the first time,developed an Sq geomagnetic field model that is directly built on the physical mechanism of the ionospheric dynamo,which is responsible for daily variations of the geomagnetic field.The performance in Sq geomagnetic field modeling was investigated using the Macao Science Satellite-1(MSS-1)data.Our model can enhance the physics-based framework of comprehensive geomagnetic field modeling for the MSS-1 and ensuing missions.
基金funded by NSFC under grants 12250014, 42250101 and 12403068supported by youth funding of Jiangsu province BK20241707+1 种基金supported by the Macao FoundationXinjiang Uygur Autonomous Region for the support through “Tianchi Talent” special expert project。
文摘Strong flares and/or coronal mass ejections(CMEs) could bring us disastrous space weather,destroy crucial technology in space,and cause a large-scale blackout during some extreme cases.They frequently cause geomagnetic storms,which is a sudden disturbance of the Earth's magnetosphere.It is well accepted that CMEs play a dominant role in causing geomagnetic storms by a direct impact,but it is still not very clear regarding their association with solar flares.The association would be helpful for forecasting geomagnetic storms directly from flares,which are much easier to observe.The Macao Science Satellite-1(MSS-1) mission,with the scientific aim of studying the origin and evolution of the geomagnetic field,is able to accurately measure the vector geomagnetic field.Besides,it measures rapid spectral evolution of the solar X-ray irradiance of solar flares.In this study,we analyzed measurements by MSS-1 during a series of X-class flares in October of 2024,and saw the relationship between the flares and the associated geomagnetic storms.The observations support that the major geomagnetic storms tend to be associated with flares' duration in addition to flare class.We also find that long duration ones have radiated more energy in the extreme ultraviolet waveband.Being equally important,our results show that the magnetic fields measured by MSS-1,especially its external(e_(1)^(0)) coefficient,can well be used for monitoring the geomagnetic disturbance.
基金supported by the National Key R&D Program of China (Grant No.2022YFF0503700)the special funds of Hubei Luojia Laboratory (Grant No.220100011)+1 种基金supported by the International Space Science Institute–Beijing(ISSI-BJ) project“The Electromagnetic Data Validation and Scientific Application Research based on CSES Satellite”and ISSI/ISSI-BJ project,“Multi-Scale Magnetosphere–Ionosphere–Thermosphere Interaction.”
文摘The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations.
基金supported by the National Research and Innovation Agency(BRIN),Indonesia.
文摘Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked to equatorial plasma bubbles(EPBs),regions of depleted plasma density that form after sunset.Ionospheric scintillation typically occurs from post-sunset hours until midnight.Post-sunset EPBs can be enhanced or suppressed during geomagnetic storms,depending on local sunset timing and how it relates to the storm's main or recovery phases.This study analyzes ionospheric scintillation in Indonesia,located at low geomagnetic and geographic latitudes,during geomagnetic events from 2003 to 2024.Using the S4 index,scintillation was examined with data from seven observation stations during geomagnetic storm events.Geomagnetic activity was evaluated using Dst,SYM-H,and AE indices,employing Superposed Epoch Analysis(SEA)to assess scintillation occurrence linked to minimum SYM-H,defined as epoch 0 to represent the storm peak or the onset of recovery phase in each event.The analysis categorized geomagnetic storms into weak-moderate(–100 nT<min.Dst≤–30 nT)and strong(min.Dst≤–100 nT),and examined their dependence on the local time of minimum SYM-H.Results indicate that scintillation first appears~6 hours after epoch 0 in weak-moderate geomagnetic storms,and~12 hours after epoch 0 in strong geomagnetic storms.The average AE index returns to its baseline value(quiet condition)~6 and~12 hours after epoch 0 for weak-moderate and strong geomagnetic storms,respectively.Further analysis based on the classification of the local time of epoch 0 shows that scintillation occurrence is not observed in post-sunset hours when epoch 0 falls between 16:00 and 19:00 LT for weak-moderate geomagnetic storms.In strong geomagnetic storms,scintillation occurrence during post-sunset hours is absent when epoch 0 is between 10:00 and 19:00 LT.Notably,when the minimum SYM-H(epoch 0)nearly coincides with local sunset,scintillation activity occurs around sunset in both weak-moderate and strong geomagnetic storms.Furthermore,when epoch 0 falls within midnight until early morning,scintillation can be generated in the post-sunset hours before epoch 0.Still,post-midnight scintillation is not observed in the equatorial region during the recovery phase of either weak-moderate and strong storm events.Our findings show that when sunset falls before or coincide with epoch 0,the likelihood of post-sunset EPB and scintillation increases,due to the prompt-penetration electric field(PPEF)in the main phase of storm.The disturbance dynamo electric field(DDEF)in the recovery phase driven by equatorward winds from auroral Joule heating operates for at least 6-and 12-hours post-epoch 0 in the cases of weak-moderate and strong geomagnetic storms,respectively.When the local sunset falls within these operational DDEF periods,post-sunset EPBs will likely be suppressed,inhibiting ionospheric scintillation during post-sunset hours.Finally,this study provides essential information for developing more accurate ionospheric scintillation prediction models in space weather services in equatorial regions.
基金supported by a Collaborative Project of the National Natural Science Foundation of China on Technical Maintenance and Data Preprocessing of the GPS Observation Array for the Qiaojia Earthquake(No.0120603)the National Natural Science Foundation of China(No.41274079).
文摘This study systematically analyzed the spatiotemporal evolution characteristics of geomagnetic anomalies before and after the 2013 Sichuan Lushan M7.0 earthquake and the Gansu Minxian M6.6 earthquake by constructing a geomagnetic diurnal variation model based on Taylor polynomial fitting,combined with midnight mean values of the geomagnetic F component from China,s geomagnetic observatory network.The results reveal distinct differences in anomaly patterns,namely per-sistent positive anomalies were observed in the epicentral region of the Lushan earthquake,while significant negative anomalies characterized the Minxian earthquake zone.This differential response reveals the modulating effect of the electrical structure of the seismogenic medium on space electromagnetic disturbances,namely positive anomalies may correspond to the stage of stable stress accumulation in intact rock,while the expansion of negative anomalies may reflect an amplification of electromagnetic disturbances induced by fracture expansion.Further analysis demonstrates that both anomalies exhibit a three-stage evolutionary pattern,namely pre-seismic accumulation,co-seismic release,and post-seismic adjustment.The phase transitions in these anomalies are closely correlated with regional tectonic stress accumulation and destabilization processes.These findings not only provide new evidence for the physical interpretation of seismomagnetic precursors but also establish a theoretical foundation for developing earthquake prediction methods based on the dynamic evolution of geomagnetic anomalies.
文摘Proper knowledge of the nature of geomagnetic storms and their relationships with the conditions of the space environment at the outer part of the Earth's magnetosphere(bow shock nose) is essential to increase our resilience to space weather disturbances. In this article, we present an analysis of the interplanetary magnetic field(IMF) and solar wind parameters relevant to 100 geomagnetic storms in Solar Cycle 24. We revisit the relationship between the minimum disturbance storm time index(Dst_(min)), the minimum southward IMF(B_(S, min)), the maximum solar wind density(N_(SW, max)) and speed(V_(max)), and the lag time between the extrema(dT(B_(z), N),dT(B_(z), V)). We end with a regression formula that fits the data, with a coefficient of determination of 0.58, a root mean square error of 21.30 nT, and a mean absolute error of 15.87 nT. Even though more complex machine learning models can outperform this model, it serves as a theoretically sensible alternative for understanding and forecasting geomagnetic storms.
基金Deep Earth Probe and Mineral Resources ExplorationNational Science and Technology Major Project(2024ZD1000208)SinoProbe Laboratory Fund of Chinese Academy of Geological Sciences(SL202401)+3 种基金Project of the Nuclear Technology Application Engineering Research Center of the Ministry of Education(HJSJYB2021-3)2022 Fuzhou Science and Technology Plan Project(Research on High Voltage Electrostatic Atomization New Air Sterilization and Purification Technology and Equipment)Jiangxi Province Major Science and Technology Special Project(20233AAE02008)Fuzhou Unveiling and Leading Project(Jiangxi Gandian)-Online Diagnosis and Intelligent Cloud Platform for the Health Status of Transformer and Distribution Equipment。
文摘Geomagnetic data hold significant value in fields such as earthquake monitoring and deep earth exploration.However,the increasing severity of anthropogenic noise contamination in existing geomagnetic observatory data poses substantial challenges to high-precision computational analysis of geomagnetic data.To overcome this problem,we propose a denoising method for geomagnetic data based on the Residual Shrinkage Network(RSN).We construct a sample library of simulated and measured geomagnetic data develop and train the RSN denoising network.Through its unique soft thresholding module,RSN adaptively learns and removes noise from the data,effectively improving data quality.In experiments with noise-added measured data,RSN enhances the quality of the noisy data by approximately 12 dB on average.The proposed method is further validated through denoising analysis on measured data by comparing results of time-domain sequences,multiple square coherence and geomagnetic transfer functions.
基金supported by the Natural Science Foundation of Shaanxi Province(Grant No.2023-JC-YB-221)。
文摘Modeling and forecasting of the geomagnetic variation are important research topics concerning geomagnetic navigation and space environment monitoring.We propose a combined forecasting model using a dynamic recursive neural network called echo state network(ESN),the method of complementary ensemble empirical mode decomposition(EEMD)and the complexity theory of sample entropy(SampEn).Firstly,we use EEMD-SampEn to decompose the geomagnetic variation time series into many series of geomagnetic variation subsequences whose complexity degrees are transparently different.Then,we use ESN to build a forecasting model for each subsequence,selecting the optimal model parameters.Finally,we use the real data collected from the geomagnetic observatory to conduct simulations.The results show that the forecasting value of the combined model can closely conform to the tendency of geomagnetic variation field,and is superior to the least square support vector machine(LSSVM)model.The mean absolute error of the model for three-hour forecasting is less than 1.40nT when Kp index is less than 3.
基金General Project of Basic Research Plan for Natural Sciences in Shaanxi Province,grant number 2023-JC-YB-244Youth Project of Basic Research Plan for Natural Sciences in Shaanxi Province,grant number 2024JC-YBQN-0253.
文摘Vector magnetic measurement is increasingly widely used.In order to improve the accuracy of vector magnetic measurement system on board a vehicle,researchers have proposed various calibration methods.Most of them require altering the magnetic vector in the vehicle coordinate system.Exploring the use of geomagnetic variation to change the geomagnetic vector in the vehicle coordinate system,this paper proposes a novel vector magnetic measurement calibration method.In this method,a vector magnetometer mounted on a vehicle and an accurate vector magnetometer separately measure the geomagnetic field at diff erent locations within the same area.Based on the physical principle that the geomagnetic variation at two nearby locations is equal,the calibration parameters of the magnetometer on the vehicle can be determined through a set of equations containing the measurements from the two magnetometers.The theoretical derivation and simulation experiment results demonstrate the feasibility of this method.Therefore,it can serve as a new alternative calibration method,especially in scenarios where a high degree of accuracy in the estimation of calibration parameters is not required.
基金supported by the National Natural Science Foundation of China(No.41471381)the General Project of Jiangsu Natural Science Foundation(No.BK20171410)the Major Scientific and Technological Achievements Cultivation Fund of Nanjing University of Aeronautics and Astronautics(No.1011-XBD23002)。
文摘Accurately predicting geomagnetic field is of great significance for space environment monitoring and space weather forecasting worldwide.This paper proposes a vision Transformer(ViT)hybrid model that leverages aurora images to predict local geomagnetic station component,breaking the spatial limitations of geomagnetic stations.Our method utilizes the ViT backbone model in combination with convolutional networks to capture both the large-scale spatial correlation and distinct local feature correlation between aurora images and geomagnetic station data.Essentially,the model comprises a visual geometry group(VGG)image feature extraction network,a ViT-based encoder network,and a regression prediction network.Our experimental findings indicate that global features of aurora images play a more substantial role in predicting geomagnetic data than local features.Specifically,the hybrid model achieves a 39.1%reduction in root mean square error compared to the VGG model,a 29.5%reduction compared to the ViT model and a 35.3%reduction relative to the residual network(ResNet)model.Moreover,the fitting accuracy of the model surpasses that of the VGG,ViT,and ResNet models by 2.14%1.58%,and 4.1%,respectively.
文摘Based on the existing geomagnetic diurnal variation theory and correction method,this paper makes a comprehensive analysis of the international geomagnetic quiet diurnal variation by Fourier Transform and one-dimensional Continuous Wavelet Transform.The frequency band greater than 0.2 Hz is the embodiment of the geomagnetic disturbance field in the frequency domain.Discrete Wavelet Transform is used to separate the variation,thus improving accuracy of the existing geomagnetic diurnal variation correction method.According to the characteristics of variation and Discrete Wavelet Decomposition,Sym8 wavelet is selected as the basic wavelet to decompose the data at 7 layers.The long-term and short-term variation of geomagnetic diurnal variation are effectively separated from the geomagnetic disturbance part under the condition of ensuring the fidelity.Compared with the results of Fourier Series decomposition and low-pass filter,the processing effect of Discrete Wavelet Transform is better.The effective separation and correction of short-term,long-term variation and geomagnetic disturbances can improve the quality of diurnal variation correction in marine geomagnetic measurement,reduce the error accumulation in the process of marine geomagnetic data processing,and improve the scientificity and accuracy of the current diurnal variation correction methods.
基金supported by the Space Science and Technology Innovation Fund of China(No.2016KC020028)the Fund of China Space Science and Technology(No.2017-HT-XG)。
文摘In this paper,we simulate,verify,and compare the performance of three classical geomagnetic matching aided navigation algorithms to assess their applicability to hypersonic vehicle navigation.Firstly,we introduce the various sources of the geomagnetic field.Secondly,we describe the principles and processes of the geomagnetic contour matching(MAGCOM)algorithm,iterative closest contour point(ICCP)algorithm,and Sandia inertial magnetic aided navigation(SIMAN)algorithm.Thirdly,we discuss the principles of inertial/geomagnetic integrated navigation,and propose the state and observation equations of integrated navigation.Finally,we perform a simulation of inertial/geomagnetic integrated navigation on the hypersonic boost-glide vehicle trajectory.The simulation results indicate that the real-time performance of the SIMAN algorithm can be optimized such that the matching accuracy is higher than that of the other two algorithms.At the same time,the SIMAN algorithm can achieve better stability,and though the amount of measurement noise can be larger,it can still achieve good positioning accuracy.
基金Project supported by the Space Science and Technology Innovation Fund of China(No.2016KC020028)the Fund of China Space Science and Technology(No.2017-HT-XG)。
文摘Owing to the lack of information about geomagnetic anomaly fields,conventional geomagnetic matching algorithms in near space are prone to divergence.Therefore,geomagnetic matching navigation algorithms for hypersonic vehicles are also prone to divergence or mismatch.To address this problem,we propose a multi-geomagnetic-component assisted localization(MCAL)algorithm to improve positioning accuracy using only the information of the main geomagnetic field.First,the main components of the geomagnetic field and a mathematical representation of the Earth’s geomagnetic field(World Magnetic Model 2015)are introduced.The mathematical relationships between the geomagnetic components are given,and the source of geomagnetic matching error is explained.We then propose the MCAL algorithm.The algorithm uses the intersections of the isopleths of the geomagnetic components and a decision method to estimate the real position of a carrier with high positioning accuracy.Finally,inertial/geomagnetic integrated navigation is simulated for hypersonic boost-glide vehicles.The simulation results demonstrate that the proposed algorithm can provide higher positioning accuracy than conventional geomagnetic matching algorithms.When the random error range is±30 nT,the average absolute latitude error and longitude error of the MCAL algorithm are 151 m and 511 m lower,respectively,than those of the Sandia inertial magnetic aided navigation(SIMAN)algorithm.
文摘By calculating the hourly standard deviation of the first-order differences of the horizontal geomagnetic com- ponent minute data, a new index Vr to represent the variation rate of the geomagnetic field was introduced. Vr-indices show similar trends in the temporal change at different observatories and have simultaneous peak values at the observatories cov- ering a large span geographically, which reveals that the source of geomagnetic disturbances represented by Vr is in the mag- netosphere. Based on the comparison among Vr, Kp and ap, it is found that generally Vr changes linearly with Kp and ap, which means that the rapid changes of magnetic field usually exist together with magnetic disturbances. But there are excep- tions. As Vr can be easily produced by individual observatory in quasi real time and is more sensitive to the variation rate of geomagnetic field rather than the field itself, it can be expected to serve for monitoring or predicting the geomagnetic-induced event in a quick and intuitive way.
