Non-adiabatic behaviour induced by the chorus-electron interaction is an important contributor to the radiation belt dynamics,and largely relies on wave frequency distribution.During the geomagnetic storm on August 2,...Non-adiabatic behaviour induced by the chorus-electron interaction is an important contributor to the radiation belt dynamics,and largely relies on wave frequency distribution.During the geomagnetic storm on August 2,2016,upper-band,lower-band and extremely low frequency(ELF)chorus waves were simultaneously observed within one orbit period of the Van Allen Probe B.Numerical simulations are performed to investigate the electron evolution by the observed chorus with different frequencies.The results show that various frequency chorus waves have different effects on electron dynamics.For chorus in the range f≈0.3 fce–0.7 fce,energy diffusion is the dominant process in electron evolutions.For chorus in the range 0.1 fce≤f≤0.25 fce,the pitch angle diffusion tends to be comparable to energy diffusion for Ek>0.5 MeV.For ELF chorus below 0.1 fce,the pitch angle diffusion rate is much above the energy diffusion rate,leading to potential scattering losses.展开更多
Previous studies have shown that EMIC waves occur preferentially in the afternoon sector of the magnetosphere.Here we report obliquely propagating H^(+)and He^(+)band EMIC waves detected by Van Allen Probe B in the re...Previous studies have shown that EMIC waves occur preferentially in the afternoon sector of the magnetosphere.Here we report obliquely propagating H^(+)and He^(+)band EMIC waves detected by Van Allen Probe B in the region of MLT=22.7–23.5 during the June 20,2013 substorm.Using the correlated energetic proton data,we present continuous calculations on EMIC wave growth rates along the inward orbit in the region L=5.5–4.2.The modeled growth rate shows remarkable agreement with the observed double band EMIC waves in both temporal and spatial evolutions.The current results demonstrate that H^(+)and He^(+)band EMIC waves can be simultaneously excited in the midnight sector under appropriate conditions.展开更多
Extremely low-frequency(ELF)chorus waves with frequencies below 0.1 fcecan cause the scattering losses of relativistic electrons.Previous studies have suggested that ELF chorus waves are excited by anisotropic electro...Extremely low-frequency(ELF)chorus waves with frequencies below 0.1 fcecan cause the scattering losses of relativistic electrons.Previous studies have suggested that ELF chorus waves are excited by anisotropic electrons with energies up to a few hundred ke V.Here,we report an interesting event observed using the Van Allen Probes on November 1,2012,where distinct ELF chorus waves occurred exactly corresponding to the enhancement of the plasma density.Using the correlated data of particles and plasma environments,the continuous calculation of growth rates along the satellite trajectory was conducted.The linear analysis results display a similar pattern to the observation results.To further identify the impact of the plasma density on the frequency control of ELF chorus waves,the growth rates were then calculated by only changing the value of the plasma density.The calculation results show that the growth rates move to lower frequencies with plasma density enhancement during the event.These findings indicate that the increased plasma density has a considerable impact on the wave frequency.The current study can enrich our understanding of the possible role of plasma density on the generation of ELF chorus waves.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41531072,41974212,41774194,42074198 and42004141)the Hunan Provincial Natural Science Foundation of China(Grant No.2018JJ2425)+1 种基金the Foundation of Education Bureau of Hunan Province for Distinguished Young Scientists(Grant No.20B004)the Specialized Research Fund for CAS Key Laboratories。
文摘Non-adiabatic behaviour induced by the chorus-electron interaction is an important contributor to the radiation belt dynamics,and largely relies on wave frequency distribution.During the geomagnetic storm on August 2,2016,upper-band,lower-band and extremely low frequency(ELF)chorus waves were simultaneously observed within one orbit period of the Van Allen Probe B.Numerical simulations are performed to investigate the electron evolution by the observed chorus with different frequencies.The results show that various frequency chorus waves have different effects on electron dynamics.For chorus in the range f≈0.3 fce–0.7 fce,energy diffusion is the dominant process in electron evolutions.For chorus in the range 0.1 fce≤f≤0.25 fce,the pitch angle diffusion tends to be comparable to energy diffusion for Ek>0.5 MeV.For ELF chorus below 0.1 fce,the pitch angle diffusion rate is much above the energy diffusion rate,leading to potential scattering losses.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41974212,41531072,41674166 and 41774194)the Hunan Provincial Natural Science Foundation of China(Grant No.2018JJ2425)。
文摘Previous studies have shown that EMIC waves occur preferentially in the afternoon sector of the magnetosphere.Here we report obliquely propagating H^(+)and He^(+)band EMIC waves detected by Van Allen Probe B in the region of MLT=22.7–23.5 during the June 20,2013 substorm.Using the correlated energetic proton data,we present continuous calculations on EMIC wave growth rates along the inward orbit in the region L=5.5–4.2.The modeled growth rate shows remarkable agreement with the observed double band EMIC waves in both temporal and spatial evolutions.The current results demonstrate that H^(+)and He^(+)band EMIC waves can be simultaneously excited in the midnight sector under appropriate conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.41974212,41804171,41774194,and 42004141)the Science and Technology Innovation Program of Hunan Province(Grant No.2021RC3098)+2 种基金the Natural Science Foundation of Hunan province(Grant No.2021JJ20010)the Foundation of Education Bureau of Hunan Province for Distinguished Young Scientists(Grant No.20B004)。
文摘Extremely low-frequency(ELF)chorus waves with frequencies below 0.1 fcecan cause the scattering losses of relativistic electrons.Previous studies have suggested that ELF chorus waves are excited by anisotropic electrons with energies up to a few hundred ke V.Here,we report an interesting event observed using the Van Allen Probes on November 1,2012,where distinct ELF chorus waves occurred exactly corresponding to the enhancement of the plasma density.Using the correlated data of particles and plasma environments,the continuous calculation of growth rates along the satellite trajectory was conducted.The linear analysis results display a similar pattern to the observation results.To further identify the impact of the plasma density on the frequency control of ELF chorus waves,the growth rates were then calculated by only changing the value of the plasma density.The calculation results show that the growth rates move to lower frequencies with plasma density enhancement during the event.These findings indicate that the increased plasma density has a considerable impact on the wave frequency.The current study can enrich our understanding of the possible role of plasma density on the generation of ELF chorus waves.
