Wave-particle interactions play a fundamental role in the dynamic variability of Earth’s donut-shaped radiation belts that are highly populated by magnetically trapped energetic particles and characteristically separ...Wave-particle interactions play a fundamental role in the dynamic variability of Earth’s donut-shaped radiation belts that are highly populated by magnetically trapped energetic particles and characteristically separated by the slot devoid of high energetic electrons.Owing to the continuous accumulation of high-quality wave and particle measurements from multiple satellites in geospace,the important contribution of ground-based very-low-frequency(VLF)transmitter waves to the electron dynamics in the near-Earth space has been unprecedently advanced,in addition to those established findings of the significant effects of a variety of naturally occurring magnetospheric waves.This paper focuses on the artificial modification of Earth’s inner radiation belt and slot by artificial VLF transmitter emissions.We review the global distributions of VLF transmitter waves in geospace,their scattering effects on radiation belt electrons in terms of both theoretical and observational analyses,and diffusion simulation results of wave-particle interactions along with data-model comparisons.We start with a brief review of the radiation belt electron dynamics and an introduction of anthropogenic VLF transmitter waves.Subsequently,we review the global morphology of in situ VLF transmitter waves corresponding to different transmitter locations,including their day-night asymmetry,geographic distributions,seasonal and geomagnetic activity dependence,and wave propagation features.Existed theoretical and observational analyses of electron scattering effects by VLF transmitter waves are then reviewed to approach the underlying physics that can modulate the spatio-temporal variations of the electron radiation belts.Further Fokker-Planck electron diffusion simulations and their comparisons with realistic satellite observations clearly indicate that VLF transmitter emissions can effectively remove energetic electrons to produce a radially bifurcated electron belt,thereby quantitatively confirming the direct link between operations of VLF transmitters at ground and changes of the energetic electron environment in space.We finally discuss the unsolved problems and possible future research in this area,which has important implications for potential mitigation of the natural particle radiation environment with active means.展开更多
We carried out a simultaneous study of ground-based magnetic field and lower ionospheric anomalies during major earthquakes occurring around Japan in 2010 and 2012. Ultra Low Frequency (ULF) geomagnetic field waveform...We carried out a simultaneous study of ground-based magnetic field and lower ionospheric anomalies during major earthquakes occurring around Japan in 2010 and 2012. Ultra Low Frequency (ULF) geomagnetic field waveforms of Esashi station and Very Low Frequency (VLF) Japanese transmitter (JJY) electric signal amplitude received in Moshiri station Hokkaido during nighttime (22:00-02:00 LT) were used to minimize the local interference. Twenty earthquakes having magnitude greater than 5.5 were considered for the data analysis for two years. Nighttime amplitude fluctuations and polarization from the received VLF transmitter signal amplitude and ULF magnetic field respectively were calculated to identify anomalous signatures in relation to every earthquake. We found most earthquakes analyzed indicating VLF amplitude anomalies simultaneously occurred with ULF magnetic field anomalies within a week prior to the earthquakes. Stronger anomalies were observed for larger magnitude and shallower earthquakes. Focal mechanism of earthquakes was also examined to identify the effectiveness of generating anomaly. Both VLF and ULF anomalies were observed for reverse fault type earthquakes occurring under the strong pressure in the crust. Obtained results may indicate the common anomaly source both for VLF and ULF in the lithosphere and are consistent with currently proposed Lithosphere-Atmosphere-Ionosphere (LAI) coupling scenarios during the earthquake preparation period.展开更多
We analyzed plasma perturbations occurring in the coexisting environment of powerful VLF transmitter emission, intense lightning strokes and strong seismic activity during pregnant period. The results suggest that ano...We analyzed plasma perturbations occurring in the coexisting environment of powerful VLF transmitter emission, intense lightning strokes and strong seismic activity during pregnant period. The results suggest that anomalous electron bursts with energy dispersion in the range of ~100–350 keV, forming the "wisp" signature, are due to cyclotron resonance of electrons with monochromatic waves from the powerful NWC VLF transmitters during nighttime. The intense broad band VLF emissions (up-going 0+ whistlers) are observed while the DEMETER satellite goes through the region of intense thunderstorm activities at mid-latitudes. However, the effects of intense lightning activity and pregnant earthquake have little impact on this kind of stable energy-dispersed electron structures, despite the fact that they are presumably two primary reasons for the particle precipitation in the ionosphere. The case studied here provides us a valuable opportunity to address the various sources triggering the anomalous plasma perturbations in the ionosphere.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42025404,42188101,41904144,41704162)the Fundamental Research Funds for the Central Universities(Grant Nos.2042021kf1045,2042021kf1056)+1 种基金the B-type Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the Pre-research projects on Civil Aerospace Technologies(Grant Nos.D020308,D020104&D020303).
文摘Wave-particle interactions play a fundamental role in the dynamic variability of Earth’s donut-shaped radiation belts that are highly populated by magnetically trapped energetic particles and characteristically separated by the slot devoid of high energetic electrons.Owing to the continuous accumulation of high-quality wave and particle measurements from multiple satellites in geospace,the important contribution of ground-based very-low-frequency(VLF)transmitter waves to the electron dynamics in the near-Earth space has been unprecedently advanced,in addition to those established findings of the significant effects of a variety of naturally occurring magnetospheric waves.This paper focuses on the artificial modification of Earth’s inner radiation belt and slot by artificial VLF transmitter emissions.We review the global distributions of VLF transmitter waves in geospace,their scattering effects on radiation belt electrons in terms of both theoretical and observational analyses,and diffusion simulation results of wave-particle interactions along with data-model comparisons.We start with a brief review of the radiation belt electron dynamics and an introduction of anthropogenic VLF transmitter waves.Subsequently,we review the global morphology of in situ VLF transmitter waves corresponding to different transmitter locations,including their day-night asymmetry,geographic distributions,seasonal and geomagnetic activity dependence,and wave propagation features.Existed theoretical and observational analyses of electron scattering effects by VLF transmitter waves are then reviewed to approach the underlying physics that can modulate the spatio-temporal variations of the electron radiation belts.Further Fokker-Planck electron diffusion simulations and their comparisons with realistic satellite observations clearly indicate that VLF transmitter emissions can effectively remove energetic electrons to produce a radially bifurcated electron belt,thereby quantitatively confirming the direct link between operations of VLF transmitters at ground and changes of the energetic electron environment in space.We finally discuss the unsolved problems and possible future research in this area,which has important implications for potential mitigation of the natural particle radiation environment with active means.
文摘We carried out a simultaneous study of ground-based magnetic field and lower ionospheric anomalies during major earthquakes occurring around Japan in 2010 and 2012. Ultra Low Frequency (ULF) geomagnetic field waveforms of Esashi station and Very Low Frequency (VLF) Japanese transmitter (JJY) electric signal amplitude received in Moshiri station Hokkaido during nighttime (22:00-02:00 LT) were used to minimize the local interference. Twenty earthquakes having magnitude greater than 5.5 were considered for the data analysis for two years. Nighttime amplitude fluctuations and polarization from the received VLF transmitter signal amplitude and ULF magnetic field respectively were calculated to identify anomalous signatures in relation to every earthquake. We found most earthquakes analyzed indicating VLF amplitude anomalies simultaneously occurred with ULF magnetic field anomalies within a week prior to the earthquakes. Stronger anomalies were observed for larger magnitude and shallower earthquakes. Focal mechanism of earthquakes was also examined to identify the effectiveness of generating anomaly. Both VLF and ULF anomalies were observed for reverse fault type earthquakes occurring under the strong pressure in the crust. Obtained results may indicate the common anomaly source both for VLF and ULF in the lithosphere and are consistent with currently proposed Lithosphere-Atmosphere-Ionosphere (LAI) coupling scenarios during the earthquake preparation period.
基金supported by the National Natural Science Foundation of China (Grant No. 41431071)
文摘We analyzed plasma perturbations occurring in the coexisting environment of powerful VLF transmitter emission, intense lightning strokes and strong seismic activity during pregnant period. The results suggest that anomalous electron bursts with energy dispersion in the range of ~100–350 keV, forming the "wisp" signature, are due to cyclotron resonance of electrons with monochromatic waves from the powerful NWC VLF transmitters during nighttime. The intense broad band VLF emissions (up-going 0+ whistlers) are observed while the DEMETER satellite goes through the region of intense thunderstorm activities at mid-latitudes. However, the effects of intense lightning activity and pregnant earthquake have little impact on this kind of stable energy-dispersed electron structures, despite the fact that they are presumably two primary reasons for the particle precipitation in the ionosphere. The case studied here provides us a valuable opportunity to address the various sources triggering the anomalous plasma perturbations in the ionosphere.
