Plasma density is an important factor in determining wave-particle interactions in the magnetosphere.We develop a machine-learning-based electron density(MLED)model in the inner magnetosphere using electron density da...Plasma density is an important factor in determining wave-particle interactions in the magnetosphere.We develop a machine-learning-based electron density(MLED)model in the inner magnetosphere using electron density data from Van Allen Probes between September 25,2012 and August 30,2019.This MLED model is a physics-based nonlinear network that employs fundamental physical principles to describe variations of electron density.It predicts the plasmapause location under different geomagnetic conditions,and models separately the electron densities of the plasmasphere and of the trough.We train the model using gradient descent and backpropagation algorithms,which are widely used to deal effectively with nonlinear relationships among physical quantities in space plasma environments.The model gives explicit expressions with few parameters and describes the associations of electron density with geomagnetic activity,solar cycle,and seasonal effects.Under various geomagnetic conditions,the electron densities calculated by this model agree well with empirical observations and provide a good description of plasmapause movement.This MLED model,which can be easily incorporated into previously developed radiation belt models,promises to be very helpful in modeling and improving forecasting of radiation belt electron dynamics.展开更多
A concise and elegant expression of cyclotron harmonic resonant quasi-pure pitch-angle diffusion is constructed for the parallel whistler mode waves, and the quasi-linear diffusion coefficient is prescribed in terms o...A concise and elegant expression of cyclotron harmonic resonant quasi-pure pitch-angle diffusion is constructed for the parallel whistler mode waves, and the quasi-linear diffusion coefficient is prescribed in terms of the whistler mode wave spectral intensity. Numerical computations are performed for the specific case of energetic electrons interacting with a band of frequency of whistler mode turbulence at L ≈ 3. It is found that the quasi-pure pitch-angle diffusion driven by the whistler mode scatters energetic electrons from the larger pitch-angles into the loss cone, and causes pitch-angle distribution to evolve from the pancake-shaped before the terrestrial storms to the flat-top during the main phase. This probably accounts for the quasi-isotropic pitch-angle distribution observed by the combined release and radiation effects satellite spacecraft at L ≈ 3.展开更多
In the past two years,many progresses were made in magnetospheric physics by the data of OMNI,SuperMAG networks,Double Star Program,Cluster,THEMIS,RBSP,DMSP,DEMETER,NOAA,Van Allen Probes,GOES,Geotail,Swarm,MMS,BeiDa,F...In the past two years,many progresses were made in magnetospheric physics by the data of OMNI,SuperMAG networks,Double Star Program,Cluster,THEMIS,RBSP,DMSP,DEMETER,NOAA,Van Allen Probes,GOES,Geotail,Swarm,MMS,BeiDa,Fengyun,ARTEMIS,MESSENGER,Juno,Chinese Mars ROVER,MAVEN,Tianwen-1,Venus Express,Lunar Prospector e.g.,or by computer simulations.This paper briefly reviews these works based on 356 papers published from January 2020 to December 2021.The subjects covered various sub-branches of Magnetospheric Physics,including solar wind-magnetosphere-ionosphere interaction,inner magnetosphere,outer magnetosphere,magnetic reconnection,planetary magnetosphere.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
基金This work is supported by the National Natural Science Foundation of China grants 42074198,41774194,41974212 and 42004141Natural Science Foundation of Hunan Province 2021JJ20010+1 种基金Science and Technology Innovation Program of Hunan Province 2021RC3098Foundation of Education Bureau of Hunan Province for Distinguished Young Scientists 20B004.
文摘Plasma density is an important factor in determining wave-particle interactions in the magnetosphere.We develop a machine-learning-based electron density(MLED)model in the inner magnetosphere using electron density data from Van Allen Probes between September 25,2012 and August 30,2019.This MLED model is a physics-based nonlinear network that employs fundamental physical principles to describe variations of electron density.It predicts the plasmapause location under different geomagnetic conditions,and models separately the electron densities of the plasmasphere and of the trough.We train the model using gradient descent and backpropagation algorithms,which are widely used to deal effectively with nonlinear relationships among physical quantities in space plasma environments.The model gives explicit expressions with few parameters and describes the associations of electron density with geomagnetic activity,solar cycle,and seasonal effects.Under various geomagnetic conditions,the electron densities calculated by this model agree well with empirical observations and provide a good description of plasmapause movement.This MLED model,which can be easily incorporated into previously developed radiation belt models,promises to be very helpful in modeling and improving forecasting of radiation belt electron dynamics.
基金Supported by the Natiopal Natural Science Foundation of China under Grant Nos 40474064 and 40404012, the Scientific Research Foundation for R0CS of the Ministry of Education of China, and the Youth Foundation of Education Bureau of Hunan Province under Grant No 04B003.
文摘A concise and elegant expression of cyclotron harmonic resonant quasi-pure pitch-angle diffusion is constructed for the parallel whistler mode waves, and the quasi-linear diffusion coefficient is prescribed in terms of the whistler mode wave spectral intensity. Numerical computations are performed for the specific case of energetic electrons interacting with a band of frequency of whistler mode turbulence at L ≈ 3. It is found that the quasi-pure pitch-angle diffusion driven by the whistler mode scatters energetic electrons from the larger pitch-angles into the loss cone, and causes pitch-angle distribution to evolve from the pancake-shaped before the terrestrial storms to the flat-top during the main phase. This probably accounts for the quasi-isotropic pitch-angle distribution observed by the combined release and radiation effects satellite spacecraft at L ≈ 3.
文摘In the past two years,many progresses were made in magnetospheric physics by the data of OMNI,SuperMAG networks,Double Star Program,Cluster,THEMIS,RBSP,DMSP,DEMETER,NOAA,Van Allen Probes,GOES,Geotail,Swarm,MMS,BeiDa,Fengyun,ARTEMIS,MESSENGER,Juno,Chinese Mars ROVER,MAVEN,Tianwen-1,Venus Express,Lunar Prospector e.g.,or by computer simulations.This paper briefly reviews these works based on 356 papers published from January 2020 to December 2021.The subjects covered various sub-branches of Magnetospheric Physics,including solar wind-magnetosphere-ionosphere interaction,inner magnetosphere,outer magnetosphere,magnetic reconnection,planetary magnetosphere.
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.
