During geomagnetically active times such as geomagnetic storms,large amounts of energy can be released into the Earth’s magnetosphere and change the ring current intensity.Previous studies showed that significant enh...During geomagnetically active times such as geomagnetic storms,large amounts of energy can be released into the Earth’s magnetosphere and change the ring current intensity.Previous studies showed that significant enhancement of the ring current was related to geomagnetic storms,while few studies have examined substorm effects on ring current dynamics.In this study,we examine the ring current variation during non-storm time(SYM-H>−50 nT)substorms,especially during super-substorms(AE>1000 nT).We perform a statistical analysis of ring current plasma pressure and number flux of various ion species under different substorm conditions,based on Van Allen Probe observations.The plasma pressure and ion fluxes of the ring current increased dramatically during supersubstorms,while little change was observed for substorms with AE<1000 nT.The results shown in this study indicate that a non-storm time super-substorm may also have a significant contribution to the ring current.展开更多
In this paper, we present evolutions of the phase space density(PSD) spectra of ring current(RC) ions based on observations made by Van Allen Probe B during a geomagnetic storm on 23–24 August 2016. By analyzing PSD ...In this paper, we present evolutions of the phase space density(PSD) spectra of ring current(RC) ions based on observations made by Van Allen Probe B during a geomagnetic storm on 23–24 August 2016. By analyzing PSD spectra ratios from the initial phase to the main phase of the storm, we find that during the main phase, RC ions with low magnetic moment μ values can penetrate deeper into the magnetosphere than can those with high μ values, and that the μ range of PSD enhancement meets the relationship: S(O^+) >S(He^+)>S(H^+). Based on simultaneously observed ULF waves, theoretical calculation suggests that the radial transport of RC ions into the deep inner magnetosphere is caused by drift-bounce resonance interactions, and the efficiency of these resonance interactions satisfies the relationship: η(O^+) > η(He^+) > η(H^+), leading to the differences in μ range of PSD enhancement for different RC ions. In the recovery phase,the observed decay rates for different RC ions meet the relationship: R(O^+) > R(He^+) > R(H^+), in accordance with previous theoretical calculations, i.e., the charge exchange lifetime of O^+ is shorter than those of H^+ and He^+.展开更多
Electromagnetic ion cyclotron(EMIC)waves are widely believed to play an important role in influencing the radiation belt and ring current dynamics.Most studies have investigated the effects or characteristics of EMIC ...Electromagnetic ion cyclotron(EMIC)waves are widely believed to play an important role in influencing the radiation belt and ring current dynamics.Most studies have investigated the effects or characteristics of EMIC waves by assuming their left-handed polarization.However,recent studies have found that the reversal of polarization,which occurs at higher latitudes along the wave propagation path,can change the wave-induced pitch angle diffusion coefficients.Whether such a polarization reversal can influence the global ring current dynamics remains unknown.In this study,we investigate the ring current dynamics and proton precipitation loss in association with polarization-reversed EMIC waves by using the ring current-atmosphere interactions model(RAM).The results indicate that the polarization reversal of H-band EMIC waves can truly decrease the scattering rates of protons of 10 to 50 keV or>100 keV in comparison with the scenario in which the EMIC waves are considered purely left-handed polarized.Additionally,the global ring current intensity and proton precipitation may be slightly affected by the polarization reversal,especially during prestorm time and the recovery phase,but the effects are not large during the main phase.This is probably because the H-band EMIC waves contribute to the proton scattering loss primarily at E<10 keV,an energy range that is not strongly affected by the polarization reversal.展开更多
The local time dependence of the geomagnetic disturbances during magnetic storms indicates the necessity of forecasting the localized magnetic storm indices.For the first time,we construct prediction models for the Su...The local time dependence of the geomagnetic disturbances during magnetic storms indicates the necessity of forecasting the localized magnetic storm indices.For the first time,we construct prediction models for the SuperMAG partial ring current indices(SMR-LT),with the advance time increasing from 1 h to 12 h by Long Short-Term Memory(LSTM)neural network.Generally,the prediction performance decreases with the advance time and is better for the SMR-06 index than for the SMR-00,SMR-12,and SMR-18 index.For the predictions with 12 h ahead,the correlation coefficient is 0.738,0.608,0.665,and 0.613,respectively.To avoid the over-represented effect of massive data during geomagnetic quiet periods,only the data during magnetic storms are used to train and test our models,and the improvement in prediction metrics increases with the advance time.For example,for predicting the storm-time SMR-06 index with 12 h ahead,the correlation coefficient and the prediction efficiency increases from 0.674 to 0.691,and from 0.349 to 0.455,respectively.The evaluation of the model performance for forecasting the storm intensity shows that the relative error for intense storms is usually less than the relative error for moderate storms.展开更多
The Substorm Current Wedge （SCW） occurrence in the late growth and onset phases of substorms was proposed as the current system which disrupts cross-tail current by diverting it to the ionosphere. The closure curren...The Substorm Current Wedge （SCW） occurrence in the late growth and onset phases of substorms was proposed as the current system which disrupts cross-tail current by diverting it to the ionosphere. The closure current for the SCW originally was suggested to be the strong westward auroral electrojet （WEJ）. However, the SCW-WEJ system has no viable generator current. Similarly, the asymmetric or Partial Ring Current （PRC） increases in strength during the growth phase, and is sometimes associated with an enhanced Region 2 field-aligned current （FAC） closing to the ionosphere, but specifics of that closure have been lacking. Here we present a tmifying picture which includes the SCW post- and pre-midnight （AM and PM, respectively） currents and a generator current in the midnight portion of the PRC system, with these currents based upon a model of the nightside magnetotail magnetic geometry. That geometry consists of open north and south lobe regions surrounding a plasmasheet with two types of closed field line regions-stretched lines in the central part of the plasmasheet （SPS） and dipolar lines （DPS） between the low lati- tude boundary layer （LLBL） regions and the SPS. There is also an important plasmasheet transition region （TPS） in which the dipolar field near the plasmapause gradually transforms to stretched lines near the earthward edge of the SPS, and in which the midnight part of the PRC flows. We propose that our proposed near-onset current system consists of a central current which be- comes part of the midnight sector PRC and which is the generator, to which are linked two three-part current systems, one on the dawnside and one on the duskside. The three-part systems consist of up and down FACs closing as Pedersen currents in the iono- sphere. These 3-part systems are not activated until near-onset is reached, because of a lack of ionospheric conductivity in the appropriate locations where the Pedersen current closure occurs. The initial downward FAC of the 3-part dawnside system and the final upward FAC of the 3-part duskside system correspond to the AM and PM current segments, respectively, of the originally proposed SCW.展开更多
In this study,we present a comprehensive evaluation of the magnetic field measurements from the Vector Field Magnetometer(VFM)aboard the recently launched Macao Science Satellite-1(MSS-1).One-year data from November 2...In this study,we present a comprehensive evaluation of the magnetic field measurements from the Vector Field Magnetometer(VFM)aboard the recently launched Macao Science Satellite-1(MSS-1).One-year data from November 2,2023,to November 1,2024,are considered.The MSS-1 flies with a low inclination(41°)and is designed to provide high-resolution magnetic field measurements,especially for monitoring the evolution of the South Atlantic Anomaly.Earlier studies confirmed the possibility of using MSS-1A data to model the Earth’s main magnetic field(e.g.,Jiang Y et al.,2024).Therefore,in this study we focus on the magnetic signatures related to the external field,which are primarily associated with magnetospheric and ionospheric currents.The global distributions of the magnetic residuals from MSS-1A show a pattern consistent with that derived from the European Space Agency’s Swarm A satellite.A statistical survey of the conjugated observations(withΔt<5 min andΔR<150 km)between the two satellites showed that the difference between their magnetic residuals is within±3 nanoteslas.By separating the magnetic residuals at the noon and midnight hours,we see that the MSS-1A data can effectively capture features of the magnetospheric and ionospheric currents,such as the magnetospheric ring current and ionospheric equatorial electrojet.Moreover,the magnetic residuals from MSS-1A show a diamagnetic effect caused by post-sunset equatorial plasma bubbles,which also suggests that the MSS-1A data have the potential to reveal the ionospheric structures.The comprehensive evaluations performed within this study demonstrate that the MSS-1A provides high-quality magnetic field data reaching the level of the Swarm satellite,which enables a deeper understanding of the modeling of Earth’s magnetic field as well as monitoring of the magnetic environment.展开更多
Supercapacitors,comprising electrical double-layer capacitors(EDLCs)and pseudocapa-citors,are widely acknowledged as high-power energy storage devices.However,their local structures and fundamental mechanisms remain p...Supercapacitors,comprising electrical double-layer capacitors(EDLCs)and pseudocapa-citors,are widely acknowledged as high-power energy storage devices.However,their local structures and fundamental mechanisms remain poorly understood,and suitable experimental techniques for investigation are also lacking.Recently,nuclear magnetic resonance(NMR)has emerged as a powerful tool for addressing these fundamental issues with high local sensitivity and non-invasiveness.In this paper,we first review the limi-tations of existing characterization methods and highlight the advantages of NMR in investigating mechanisms of supercapacitors.Subsequently,we introduce the basic prin-ciple of ring current effect,NMR-active nuclei,and various NMR techniques employed in exploring energy storage mechanisms including cross polarization(CP)magic angle spinning(MAS)NMR,multiple-quantum(MQ)MAS,two-dimensional exchange spec-troscopy(2D-EXSY)NMR,magnetic resonance imaging(MRI)and pulsed-field gradient(PFG)NMR.Based on this,recent progress in investigating energy storage mechanisms in EDLCs and pseudocapacitors through various NMR techniques is discussed.Finally,an outlook on future directions for NMR research in supercapacitors is offered.展开更多
The gyroresonant interaction between electromagnetic ion cyclotron （EMIC） waves and energetic particles was studied in a multi-ion （H^＋, He^＋, and O^＋） plasma. The minimum resonant energy Emin, resonant wave fr...The gyroresonant interaction between electromagnetic ion cyclotron （EMIC） waves and energetic particles was studied in a multi-ion （H^＋, He^＋, and O^＋） plasma. The minimum resonant energy Emin, resonant wave frequency w, and pitch angle diffusion coefficient Daa were calculated at the center location of the symmetrical ring current： r ≈3.5RE with RE the Earth＇s radius. Emin is found to decrease rapidly from 10 MeV to a few keV with the increase in ca in three bands： H^＋-band, He^＋-band and O^＋-band. Moreover, EMIC waves have substantial potential to scatter energetic （～100 keV） ions （mainly H^＋ and He^＋） into the loss cone and yield precipitation loss, suggesting that wave-particle interactions contribute to ring current decay.展开更多
The attosecond ionization dynamics of atoms has attracted extensive attention in these days.However,the role of the initial state is not clearly understood.To address this question,we perform simulations on the neon a...The attosecond ionization dynamics of atoms has attracted extensive attention in these days.However,the role of the initial state is not clearly understood.To address this question,we perform simulations on the neon atom and its model atom with different initial states by numerically solving the corresponding two-dimensional time-dependent Schrodinger¨equations.We theoretically investigate atomic photoelectron momentum distributions(PMDs)by a pair of elliptically polarized attosecond laser pulses.We find that the PMD is sensitive not only to the ellipticities of the pulses,the relative helicity,and time delay of the pulses,but also to the symmetry of the initial electronic states.Results are analyzed by the first-order time-dependent perturbation theory(TDPT)and offer a new tool for detecting the rotation direction of the ring currents.展开更多
Coherent electronic dynamics are of great significance in photo-induced processes and molecular magnetism.We theoretically investigate electronic dynamics of triatomic molecule H_(3)^(2+) by circularly polarized pulse...Coherent electronic dynamics are of great significance in photo-induced processes and molecular magnetism.We theoretically investigate electronic dynamics of triatomic molecule H_(3)^(2+) by circularly polarized pulses,including electron density distributions,induced electronic currents,and ultrafast magnetic field generation.By comparing the results of the coherent resonant excitation and direct ionization,we found that for the coherent resonant excitation,the electron is localized and the coherent electron wave packet moves periodically between three protons,which can be attributed to the coherent superposition of the ground A′state and excited E+state.Whereas,for the direct single-photon ionization,the induced electronic currents mainly come from the free electron in the continuum state.It is found that there are differences in the intensity,phase,and frequency of the induced current and the generated magnetic field.The scheme allows one to control the induced electronic current and the ultrafast magnetic field generation.展开更多
Geosynchronous orbit is located in the ring current region,where the energetic particle emission environment challenges the ion deflection design limit of the Energetic Neutral Atom(ENA)imager.Therefore,there is no me...Geosynchronous orbit is located in the ring current region,where the energetic particle emission environment challenges the ion deflection design limit of the Energetic Neutral Atom(ENA)imager.Therefore,there is no measurement record of ENA imaging in this area before.On the basis of possessing the patent of high-energy ion deflection technology,ENA imaging under different Kp index in geosynchronous orbit is simulated.The simulation images show the characteristics of low-altitude ENA emission source and the rough sketch of magnetosphere.Due to the north-south conjugation observation of geosynchronous orbit,the simulated ENA images at different positions all have north-south symmetry.Aiming at the unsolved problems,such as the input source of ring current energetic ions during geomagnetic activities and its evolution process,we analyzed the possible results of ENA imaging combined with in-situ particle measurements in the same satellite,as well as the subversion effect of any north-south asymmetry of ENA map on the inversion model.展开更多
Comprehensive records are available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm （which incorporated a series of substorms）. Ion flu...Comprehensive records are available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm （which incorporated a series of substorms）. Ion fluxes at 4-min temporal resolution derived from ENA data in the energy ranges 50-81 and 81-158 keV are compared with in situ particle fluxes measured by the LANL-SOPA instruments aboard LANL-01, LANL-02, LANL-97, and LANL-84 （a series of geostationary satellites that encircle the equatorial plane at -6.6 RE）. Also, magnetic fields measured simultaneously by the magetometers aboard GOES-10 and GOES-12 （which are also geostationary satellites） are compared with the particle data. It is demonstrated that ion fluxes in the ring current were enhanced during geomagnetic field tailward stretching in the growth phases of substorms rather than after Earthward directed dipolarization events. This observation, which challenges the existing concept that ring current particles are injected Earthward from the magnetotail following dipolarization events, requires further investigation using a large number of magnetic storm events.展开更多
The azimuthal morphology of Earth's ring currents has consistently shown asymmetry during extreme space weather events at low latitudes,particularly during geomagnetic storms.A dawn-dusk pattern has been detected ...The azimuthal morphology of Earth's ring currents has consistently shown asymmetry during extreme space weather events at low latitudes,particularly during geomagnetic storms.A dawn-dusk pattern has been detected during the storm main phase through near-Earth and in-situ magnetic measurements.This asymmetry is believed to arise from asymmetric solar windmagnetosphere coupling and is linked to the closure of the ring current.Recent evidence has confirmed the existence of asymmetric ring currents during quiet times and the storm recovery phase.This phenomenon may be closely related to the evolution of ring currents,including plasma injection and decay processes.In this study,the local time asymmetry of the ring current is estimated using data from low-Earth-orbit Swarm and Macao Science Satellite-1(MSS-1)missions.Spherical harmonics models are developed to quantify the magnetic field of ring currents through external Gauss coefficients during both quiet periods and the storm recovery phase.Several features of dawn-dusk asymmetry are observed in various cases in different months.(1)The maximum difference in magnetic value across local time ranges from 3 to 10 nT,showing relative invariance compared with various Sym-H levels.(2)Stronger magnetic signals are detected at the premidnight sector during quiet times and at the afternoon sector during the storm recovery phase.(3)Magnetic perturbations remain at a lower level during the postmidnight and morning sectors.Although the pattern of local time asymmetry differs between quiet times and the recovery phase,dawn-dusk asymmetry remains the most pronounced feature,affecting the trapping and loss of charged particles in the inner magnetosphere.Combining Swarm and MSS-1 magnetic observations can enable convenient monitoring of the detailed azimuthal local time effects of the ring current at various disturbance levels in the future.展开更多
Among the most intense emissions in the Earth's magnetosphere,electromagnetic ion cyclotron(EMIC)waves are regarded as a critical candidate contributing to the precipitation losses of ring current protons,which ho...Among the most intense emissions in the Earth's magnetosphere,electromagnetic ion cyclotron(EMIC)waves are regarded as a critical candidate contributing to the precipitation losses of ring current protons,which however lacks direct multi-point observations to establish the underlying physical connection.Based upon a robust conjunction between the satellite pair of Van Allen Probe B and NOAA-19,we perform a detailed analysis to capture simultaneous enhancements of EMIC waves and ring current proton precipitation.By assuming that the ring current proton precipitation is mainly caused by EMIC wave scattering,we establish a physical model between the wave-driven proton diffusion and the ratio of precipitated-to-trapped proton count rates,which is subsequently applied to infer the intensity of EMIC waves required to cause the observed proton precipitation.Our simulations indicate that the model results of EMIC wave intensity,obtained using either the observed or empirical Gaussian wave frequency spectrum,are consistent with the wave observations,within a factor of 1.5.Our study therefore strongly supports the dominant contribution of EMIC waves to the ring current proton precipitation,and offers a valuable means to construct the global profile of EMIC wave intensity using low-altitude NOAA POES proton measurements,which generally have a broad L-shell coverage and high time resolution in favor of near-real-time conversion of the global EMIC wave distribution.展开更多
The ring current,one of the most important current systems around the Earth,intensifies during geomagnetic storms and is believed to be the main reason for large-scale magnetic field perturbations in the geospace envi...The ring current,one of the most important current systems around the Earth,intensifies during geomagnetic storms and is believed to be the main reason for large-scale magnetic field perturbations in the geospace environment.Understanding how the ring current builds up and evolves during geomagnetic storms is of great importance not only for advancing the knowledge of the Sun-Earth system but also for improving the modeling capability of predicting hazardous space weather events.Focusing on the national strategic needs in the space weather prediction,in this study,we establish a ring current model named storm time ring current model(STRIM).The STRIM comprehensively embraces key physical processes in association with ring current dynamics,including plasma source injections from the nightside plasmasheet and transport around the Earth,charge-exchange with neutral hydrogens,Coulomb collisions with thermal plasma,wave-particle interactions,field line curvature scattering,and precipitation loss down to the upper atmosphere.The electric fields needed for particle motion can be optionally taken from empirical models or self-consistently calculated,while the magnetic field configuration is obtained from Tsyganenko 2005 model.Simulation results are verified against the published literature and validated with in-situ satellite or ground-based observations and are found to have the same high-level capability and fidelity as other well-known published models.We also discuss future tasks of fostering the model's performance and potential applications.展开更多
We present evidence of geomagnetic storms in Mercury’s magnetosphere based on MESSENGER magnetic field observations made just before the probe impacted the planet.Our findings answer the question of whether geomagnet...We present evidence of geomagnetic storms in Mercury’s magnetosphere based on MESSENGER magnetic field observations made just before the probe impacted the planet.Our findings answer the question of whether geomagnetic storms can occur in other planetary magnetospheres.The interaction of the solar wind with Mercury’s magnetosphere is known to involve flux transfer events in the dayside magnetosphere,plasmoids and flux ropes in the magnetotail,and substorm-like processes,all of which occur morphologically similar to Earth but with significant differences.The significantly weaker magnetic field,smaller magnetosphere,and much faster timescale of processes around Mercury,when compared with Earth,enable charged particles to escape its magnetosphere more efficiently through magnetopause shadowing and direct bombard of the surface.Our analysis of MESSENGER’s data during a coronal mass ejection(CME)proves that,despite these substantial differences,a bifurcated ring current can form in Mercury’s magnetosphere that initiates magnetic storms under strong solar wind driving.展开更多
Fine structured multiple-harmonic electromagnetic emissions at frequencies around the equatorial oxygen cyclotron harmonics are observed by Van Allen Probe A outside the core plasmasphere(L^5) off the magnetic equator...Fine structured multiple-harmonic electromagnetic emissions at frequencies around the equatorial oxygen cyclotron harmonics are observed by Van Allen Probe A outside the core plasmasphere(L^5) off the magnetic equator(MLAT~.7.5°)during a geomagnetic storm. We find that the multiple-harmonic emissions have power spectrum density(PSD) peaks during 2–8equatorial oxygen gyroharmonics( f ~ n fO+, n=2–8), while the fundamental mode(n=1) is absent, implying that the harmonic waves are generated near the equator and propagate into the observation region. Additionally, these electromagnetic emissions are linearly polarized. Different from the equatorial noise emission that propagates considerably obliquely, these emissions have moderate wave normal angles(approximately 40°–60°), which predominately increase as the harmonic number increases.Considering their frequency and wave normal angle characteristics, it is suggested that these multiple-harmonic emissions play an important role in the dynamic variation of radiation belt electrons.展开更多
基金supported by a research grant of China National Space Administration project D020303,NSFC Grant Numbers:41974191the National Key R&D Program of China 2020YFE0202100。
文摘During geomagnetically active times such as geomagnetic storms,large amounts of energy can be released into the Earth’s magnetosphere and change the ring current intensity.Previous studies showed that significant enhancement of the ring current was related to geomagnetic storms,while few studies have examined substorm effects on ring current dynamics.In this study,we examine the ring current variation during non-storm time(SYM-H>−50 nT)substorms,especially during super-substorms(AE>1000 nT).We perform a statistical analysis of ring current plasma pressure and number flux of various ion species under different substorm conditions,based on Van Allen Probe observations.The plasma pressure and ion fluxes of the ring current increased dramatically during supersubstorms,while little change was observed for substorms with AE<1000 nT.The results shown in this study indicate that a non-storm time super-substorm may also have a significant contribution to the ring current.
基金supported by the National Natural Science Foundation of China (41925018, 41874194)
文摘In this paper, we present evolutions of the phase space density(PSD) spectra of ring current(RC) ions based on observations made by Van Allen Probe B during a geomagnetic storm on 23–24 August 2016. By analyzing PSD spectra ratios from the initial phase to the main phase of the storm, we find that during the main phase, RC ions with low magnetic moment μ values can penetrate deeper into the magnetosphere than can those with high μ values, and that the μ range of PSD enhancement meets the relationship: S(O^+) >S(He^+)>S(H^+). Based on simultaneously observed ULF waves, theoretical calculation suggests that the radial transport of RC ions into the deep inner magnetosphere is caused by drift-bounce resonance interactions, and the efficiency of these resonance interactions satisfies the relationship: η(O^+) > η(He^+) > η(H^+), leading to the differences in μ range of PSD enhancement for different RC ions. In the recovery phase,the observed decay rates for different RC ions meet the relationship: R(O^+) > R(He^+) > R(H^+), in accordance with previous theoretical calculations, i.e., the charge exchange lifetime of O^+ is shorter than those of H^+ and He^+.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41974192 and 41821003)Work at Los Alamos was performed under the auspices of the U.S.Department of Energy(Contract No.89233218CNA000001)was partially funded by an NSF grant(Grant No.IAA2027951).
文摘Electromagnetic ion cyclotron(EMIC)waves are widely believed to play an important role in influencing the radiation belt and ring current dynamics.Most studies have investigated the effects or characteristics of EMIC waves by assuming their left-handed polarization.However,recent studies have found that the reversal of polarization,which occurs at higher latitudes along the wave propagation path,can change the wave-induced pitch angle diffusion coefficients.Whether such a polarization reversal can influence the global ring current dynamics remains unknown.In this study,we investigate the ring current dynamics and proton precipitation loss in association with polarization-reversed EMIC waves by using the ring current-atmosphere interactions model(RAM).The results indicate that the polarization reversal of H-band EMIC waves can truly decrease the scattering rates of protons of 10 to 50 keV or>100 keV in comparison with the scenario in which the EMIC waves are considered purely left-handed polarized.Additionally,the global ring current intensity and proton precipitation may be slightly affected by the polarization reversal,especially during prestorm time and the recovery phase,but the effects are not large during the main phase.This is probably because the H-band EMIC waves contribute to the proton scattering loss primarily at E<10 keV,an energy range that is not strongly affected by the polarization reversal.
基金Supported by National Natural Science Foundation of China grants(42022032,41874203,42188101)project of Civil Aerospace"13 th Five Year Plan"Preliminary Research in Space Science(D020301,D030202),Strategic Priority Research Program of CAS(XDA17010301)+1 种基金Key Research Program of Frontier Sciences CAS(QYZDJ-SSW-JSC028)International Partner-National Program of CAS(183311KYSB20200017)。
文摘The local time dependence of the geomagnetic disturbances during magnetic storms indicates the necessity of forecasting the localized magnetic storm indices.For the first time,we construct prediction models for the SuperMAG partial ring current indices(SMR-LT),with the advance time increasing from 1 h to 12 h by Long Short-Term Memory(LSTM)neural network.Generally,the prediction performance decreases with the advance time and is better for the SMR-06 index than for the SMR-00,SMR-12,and SMR-18 index.For the predictions with 12 h ahead,the correlation coefficient is 0.738,0.608,0.665,and 0.613,respectively.To avoid the over-represented effect of massive data during geomagnetic quiet periods,only the data during magnetic storms are used to train and test our models,and the improvement in prediction metrics increases with the advance time.For example,for predicting the storm-time SMR-06 index with 12 h ahead,the correlation coefficient and the prediction efficiency increases from 0.674 to 0.691,and from 0.349 to 0.455,respectively.The evaluation of the model performance for forecasting the storm intensity shows that the relative error for intense storms is usually less than the relative error for moderate storms.
文摘The Substorm Current Wedge （SCW） occurrence in the late growth and onset phases of substorms was proposed as the current system which disrupts cross-tail current by diverting it to the ionosphere. The closure current for the SCW originally was suggested to be the strong westward auroral electrojet （WEJ）. However, the SCW-WEJ system has no viable generator current. Similarly, the asymmetric or Partial Ring Current （PRC） increases in strength during the growth phase, and is sometimes associated with an enhanced Region 2 field-aligned current （FAC） closing to the ionosphere, but specifics of that closure have been lacking. Here we present a tmifying picture which includes the SCW post- and pre-midnight （AM and PM, respectively） currents and a generator current in the midnight portion of the PRC system, with these currents based upon a model of the nightside magnetotail magnetic geometry. That geometry consists of open north and south lobe regions surrounding a plasmasheet with two types of closed field line regions-stretched lines in the central part of the plasmasheet （SPS） and dipolar lines （DPS） between the low lati- tude boundary layer （LLBL） regions and the SPS. There is also an important plasmasheet transition region （TPS） in which the dipolar field near the plasmapause gradually transforms to stretched lines near the earthward edge of the SPS, and in which the midnight part of the PRC flows. We propose that our proposed near-onset current system consists of a central current which be- comes part of the midnight sector PRC and which is the generator, to which are linked two three-part current systems, one on the dawnside and one on the duskside. The three-part systems consist of up and down FACs closing as Pedersen currents in the iono- sphere. These 3-part systems are not activated until near-onset is reached, because of a lack of ionospheric conductivity in the appropriate locations where the Pedersen current closure occurs. The initial downward FAC of the 3-part dawnside system and the final upward FAC of the 3-part duskside system correspond to the AM and PM current segments, respectively, of the originally proposed SCW.
基金supported by the National Natural Science Foundation of China(Grant Nos.42474200 and 42174186)Chao Xiong is supported by the Dragon 6 cooperation 2024-2028(Project No.95437).
文摘In this study,we present a comprehensive evaluation of the magnetic field measurements from the Vector Field Magnetometer(VFM)aboard the recently launched Macao Science Satellite-1(MSS-1).One-year data from November 2,2023,to November 1,2024,are considered.The MSS-1 flies with a low inclination(41°)and is designed to provide high-resolution magnetic field measurements,especially for monitoring the evolution of the South Atlantic Anomaly.Earlier studies confirmed the possibility of using MSS-1A data to model the Earth’s main magnetic field(e.g.,Jiang Y et al.,2024).Therefore,in this study we focus on the magnetic signatures related to the external field,which are primarily associated with magnetospheric and ionospheric currents.The global distributions of the magnetic residuals from MSS-1A show a pattern consistent with that derived from the European Space Agency’s Swarm A satellite.A statistical survey of the conjugated observations(withΔt<5 min andΔR<150 km)between the two satellites showed that the difference between their magnetic residuals is within±3 nanoteslas.By separating the magnetic residuals at the noon and midnight hours,we see that the MSS-1A data can effectively capture features of the magnetospheric and ionospheric currents,such as the magnetospheric ring current and ionospheric equatorial electrojet.Moreover,the magnetic residuals from MSS-1A show a diamagnetic effect caused by post-sunset equatorial plasma bubbles,which also suggests that the MSS-1A data have the potential to reveal the ionospheric structures.The comprehensive evaluations performed within this study demonstrate that the MSS-1A provides high-quality magnetic field data reaching the level of the Swarm satellite,which enables a deeper understanding of the modeling of Earth’s magnetic field as well as monitoring of the magnetic environment.
基金supported by the National Natural Science Foundation of China(Grant No.22075064)National Key Laboratory Projects(No.SYSKT20230056).
文摘Supercapacitors,comprising electrical double-layer capacitors(EDLCs)and pseudocapa-citors,are widely acknowledged as high-power energy storage devices.However,their local structures and fundamental mechanisms remain poorly understood,and suitable experimental techniques for investigation are also lacking.Recently,nuclear magnetic resonance(NMR)has emerged as a powerful tool for addressing these fundamental issues with high local sensitivity and non-invasiveness.In this paper,we first review the limi-tations of existing characterization methods and highlight the advantages of NMR in investigating mechanisms of supercapacitors.Subsequently,we introduce the basic prin-ciple of ring current effect,NMR-active nuclei,and various NMR techniques employed in exploring energy storage mechanisms including cross polarization(CP)magic angle spinning(MAS)NMR,multiple-quantum(MQ)MAS,two-dimensional exchange spec-troscopy(2D-EXSY)NMR,magnetic resonance imaging(MRI)and pulsed-field gradient(PFG)NMR.Based on this,recent progress in investigating energy storage mechanisms in EDLCs and pseudocapacitors through various NMR techniques is discussed.Finally,an outlook on future directions for NMR research in supercapacitors is offered.
基金National Natural Science Foundation of China (Nos.40874076,40774078,40774079 and 40536029)the Special Fund for Public Welfare Industry (meteorology)GYHY200806072the Visiting Scholar Foundation of State Key Laboratory for Space Weather,Chinese Academy of Sciences
文摘The gyroresonant interaction between electromagnetic ion cyclotron （EMIC） waves and energetic particles was studied in a multi-ion （H^＋, He^＋, and O^＋） plasma. The minimum resonant energy Emin, resonant wave frequency w, and pitch angle diffusion coefficient Daa were calculated at the center location of the symmetrical ring current： r ≈3.5RE with RE the Earth＇s radius. Emin is found to decrease rapidly from 10 MeV to a few keV with the increase in ca in three bands： H^＋-band, He^＋-band and O^＋-band. Moreover, EMIC waves have substantial potential to scatter energetic （～100 keV） ions （mainly H^＋ and He^＋） into the loss cone and yield precipitation loss, suggesting that wave-particle interactions contribute to ring current decay.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404204 and 11974229)the Natural Science Foundation for Young Scientists of Shanxi Province,China(Grant No.201901D211404)+1 种基金the Scientific and Technological Innovation Program of Higher Education Institutions in Shanxi Province,China(Grant No.2019L0468)the Project of Excellent Course of Shanxi Normal University,China(Grant No.2017YZKC-35).
文摘The attosecond ionization dynamics of atoms has attracted extensive attention in these days.However,the role of the initial state is not clearly understood.To address this question,we perform simulations on the neon atom and its model atom with different initial states by numerically solving the corresponding two-dimensional time-dependent Schrodinger¨equations.We theoretically investigate atomic photoelectron momentum distributions(PMDs)by a pair of elliptically polarized attosecond laser pulses.We find that the PMD is sensitive not only to the ellipticities of the pulses,the relative helicity,and time delay of the pulses,but also to the symmetry of the initial electronic states.Results are analyzed by the first-order time-dependent perturbation theory(TDPT)and offer a new tool for detecting the rotation direction of the ring currents.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074146 and 12074142)。
文摘Coherent electronic dynamics are of great significance in photo-induced processes and molecular magnetism.We theoretically investigate electronic dynamics of triatomic molecule H_(3)^(2+) by circularly polarized pulses,including electron density distributions,induced electronic currents,and ultrafast magnetic field generation.By comparing the results of the coherent resonant excitation and direct ionization,we found that for the coherent resonant excitation,the electron is localized and the coherent electron wave packet moves periodically between three protons,which can be attributed to the coherent superposition of the ground A′state and excited E+state.Whereas,for the direct single-photon ionization,the induced electronic currents mainly come from the free electron in the continuum state.It is found that there are differences in the intensity,phase,and frequency of the induced current and the generated magnetic field.The scheme allows one to control the induced electronic current and the ultrafast magnetic field generation.
基金Supported by National Key R&D Program of China(2020YFE0202100)National Mission/Other National Mission:Research on Key Technologies of the Outer Heliospheric Space Exploration System(Y91 Z100102)National Mission/National Major Science and Technology Project:CE-7 Relay Satellite Display Neutral Atom Imager(E16504B31S)。
文摘Geosynchronous orbit is located in the ring current region,where the energetic particle emission environment challenges the ion deflection design limit of the Energetic Neutral Atom(ENA)imager.Therefore,there is no measurement record of ENA imaging in this area before.On the basis of possessing the patent of high-energy ion deflection technology,ENA imaging under different Kp index in geosynchronous orbit is simulated.The simulation images show the characteristics of low-altitude ENA emission source and the rough sketch of magnetosphere.Due to the north-south conjugation observation of geosynchronous orbit,the simulated ENA images at different positions all have north-south symmetry.Aiming at the unsolved problems,such as the input source of ring current energetic ions during geomagnetic activities and its evolution process,we analyzed the possible results of ENA imaging combined with in-situ particle measurements in the same satellite,as well as the subversion effect of any north-south asymmetry of ENA map on the inversion model.
基金the National Natural Science Foundation of China(Grant Nos.41431071,41574152)the National Basic Research Program of China(Grant No.2011CB811404)the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(Grant No.XDA04060201)
文摘Comprehensive records are available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm （which incorporated a series of substorms）. Ion fluxes at 4-min temporal resolution derived from ENA data in the energy ranges 50-81 and 81-158 keV are compared with in situ particle fluxes measured by the LANL-SOPA instruments aboard LANL-01, LANL-02, LANL-97, and LANL-84 （a series of geostationary satellites that encircle the equatorial plane at -6.6 RE）. Also, magnetic fields measured simultaneously by the magetometers aboard GOES-10 and GOES-12 （which are also geostationary satellites） are compared with the particle data. It is demonstrated that ion fluxes in the ring current were enhanced during geomagnetic field tailward stretching in the growth phases of substorms rather than after Earthward directed dipolarization events. This observation, which challenges the existing concept that ring current particles are injected Earthward from the magnetotail following dipolarization events, requires further investigation using a large number of magnetic storm events.
基金supported by the National Natural Science Foundation of China(Grant Nos.12250014,and 12250012)the Macao Foundation。
文摘The azimuthal morphology of Earth's ring currents has consistently shown asymmetry during extreme space weather events at low latitudes,particularly during geomagnetic storms.A dawn-dusk pattern has been detected during the storm main phase through near-Earth and in-situ magnetic measurements.This asymmetry is believed to arise from asymmetric solar windmagnetosphere coupling and is linked to the closure of the ring current.Recent evidence has confirmed the existence of asymmetric ring currents during quiet times and the storm recovery phase.This phenomenon may be closely related to the evolution of ring currents,including plasma injection and decay processes.In this study,the local time asymmetry of the ring current is estimated using data from low-Earth-orbit Swarm and Macao Science Satellite-1(MSS-1)missions.Spherical harmonics models are developed to quantify the magnetic field of ring currents through external Gauss coefficients during both quiet periods and the storm recovery phase.Several features of dawn-dusk asymmetry are observed in various cases in different months.(1)The maximum difference in magnetic value across local time ranges from 3 to 10 nT,showing relative invariance compared with various Sym-H levels.(2)Stronger magnetic signals are detected at the premidnight sector during quiet times and at the afternoon sector during the storm recovery phase.(3)Magnetic perturbations remain at a lower level during the postmidnight and morning sectors.Although the pattern of local time asymmetry differs between quiet times and the recovery phase,dawn-dusk asymmetry remains the most pronounced feature,affecting the trapping and loss of charged particles in the inner magnetosphere.Combining Swarm and MSS-1 magnetic observations can enable convenient monitoring of the detailed azimuthal local time effects of the ring current at various disturbance levels in the future.
基金supported by the National Natural Science Foundation of China (42188101 and 42025404)the National Key R&D Program of China (2022YFF0503700)+2 种基金the B-type Strategic Priority Program of the Chinese Academy of Sciences (XDB41000000)the Fundamental Research Funds for the Central Universities (2042021kf1045,2042021kf1056)the Pre-research projects on Civil Aerospace Technologies (D020308,D020104,D020303).
文摘Among the most intense emissions in the Earth's magnetosphere,electromagnetic ion cyclotron(EMIC)waves are regarded as a critical candidate contributing to the precipitation losses of ring current protons,which however lacks direct multi-point observations to establish the underlying physical connection.Based upon a robust conjunction between the satellite pair of Van Allen Probe B and NOAA-19,we perform a detailed analysis to capture simultaneous enhancements of EMIC waves and ring current proton precipitation.By assuming that the ring current proton precipitation is mainly caused by EMIC wave scattering,we establish a physical model between the wave-driven proton diffusion and the ratio of precipitated-to-trapped proton count rates,which is subsequently applied to infer the intensity of EMIC waves required to cause the observed proton precipitation.Our simulations indicate that the model results of EMIC wave intensity,obtained using either the observed or empirical Gaussian wave frequency spectrum,are consistent with the wave observations,within a factor of 1.5.Our study therefore strongly supports the dominant contribution of EMIC waves to the ring current proton precipitation,and offers a valuable means to construct the global profile of EMIC wave intensity using low-altitude NOAA POES proton measurements,which generally have a broad L-shell coverage and high time resolution in favor of near-real-time conversion of the global EMIC wave distribution.
基金supported by the National Natural Science Foundation of China(Grant Nos.41821003 and 41974192)the Fundamental Research Funds for the Central Universities。
文摘The ring current,one of the most important current systems around the Earth,intensifies during geomagnetic storms and is believed to be the main reason for large-scale magnetic field perturbations in the geospace environment.Understanding how the ring current builds up and evolves during geomagnetic storms is of great importance not only for advancing the knowledge of the Sun-Earth system but also for improving the modeling capability of predicting hazardous space weather events.Focusing on the national strategic needs in the space weather prediction,in this study,we establish a ring current model named storm time ring current model(STRIM).The STRIM comprehensively embraces key physical processes in association with ring current dynamics,including plasma source injections from the nightside plasmasheet and transport around the Earth,charge-exchange with neutral hydrogens,Coulomb collisions with thermal plasma,wave-particle interactions,field line curvature scattering,and precipitation loss down to the upper atmosphere.The electric fields needed for particle motion can be optionally taken from empirical models or self-consistently calculated,while the magnetic field configuration is obtained from Tsyganenko 2005 model.Simulation results are verified against the published literature and validated with in-situ satellite or ground-based observations and are found to have the same high-level capability and fidelity as other well-known published models.We also discuss future tasks of fostering the model's performance and potential applications.
基金supported by Major Project of Chinese National Programs for Fundamental Research and Development(Grant No.2021YFA0718600)China Space Agency Project(Grant No.D020301)+2 种基金the National Natural Science Foundation of China(Grant No.42011530080)financial support from the Canadian Space Agency and NSERCpartially supported by National Science Foundation(Grant No.AGS-1352669)。
文摘We present evidence of geomagnetic storms in Mercury’s magnetosphere based on MESSENGER magnetic field observations made just before the probe impacted the planet.Our findings answer the question of whether geomagnetic storms can occur in other planetary magnetospheres.The interaction of the solar wind with Mercury’s magnetosphere is known to involve flux transfer events in the dayside magnetosphere,plasmoids and flux ropes in the magnetotail,and substorm-like processes,all of which occur morphologically similar to Earth but with significant differences.The significantly weaker magnetic field,smaller magnetosphere,and much faster timescale of processes around Mercury,when compared with Earth,enable charged particles to escape its magnetosphere more efficiently through magnetopause shadowing and direct bombard of the surface.Our analysis of MESSENGER’s data during a coronal mass ejection(CME)proves that,despite these substantial differences,a bifurcated ring current can form in Mercury’s magnetosphere that initiates magnetic storms under strong solar wind driving.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41374168, 41521063 & 41174140)Key Grant Project of Chinese Ministry of Education (Grant No. 2042015KF0169)Program for New Century Excellent Talents in University (Grant No. NCET-13-0446)
文摘Fine structured multiple-harmonic electromagnetic emissions at frequencies around the equatorial oxygen cyclotron harmonics are observed by Van Allen Probe A outside the core plasmasphere(L^5) off the magnetic equator(MLAT~.7.5°)during a geomagnetic storm. We find that the multiple-harmonic emissions have power spectrum density(PSD) peaks during 2–8equatorial oxygen gyroharmonics( f ~ n fO+, n=2–8), while the fundamental mode(n=1) is absent, implying that the harmonic waves are generated near the equator and propagate into the observation region. Additionally, these electromagnetic emissions are linearly polarized. Different from the equatorial noise emission that propagates considerably obliquely, these emissions have moderate wave normal angles(approximately 40°–60°), which predominately increase as the harmonic number increases.Considering their frequency and wave normal angle characteristics, it is suggested that these multiple-harmonic emissions play an important role in the dynamic variation of radiation belt electrons.
