中国物理B ›› 2014, Vol. 23 ›› Issue (8): 89401-089401.doi: 10.1088/1674-1056/23/8/089401

• GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS • 上一篇    下一篇

Test particle simulations of resonant interactions between energetic electrons and discrete, multi-frequency artificial whistler waves in the plasmasphere

常珊珊, 倪彬彬, 赵正予, 顾旭东, 周晨   

  1. Department of Space Physics, School of Electronic Information, Wuhan University, Wuhan 430072, China
  • 收稿日期:2014-03-25 修回日期:2014-04-17 出版日期:2014-08-15 发布日期:2014-08-15
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 41204120 and 41304130) and the Fundamental Research Funds for the Central Universities (Grant No. 2042014kf0251).

Test particle simulations of resonant interactions between energetic electrons and discrete, multi-frequency artificial whistler waves in the plasmasphere

Chang Shan-Shan (常珊珊), Ni Bin-Bin (倪彬彬), Zhao Zheng-Yu (赵正予), Gu Xu-Dong (顾旭东), Zhou Chen (周晨)   

  1. Department of Space Physics, School of Electronic Information, Wuhan University, Wuhan 430072, China
  • Received:2014-03-25 Revised:2014-04-17 Online:2014-08-15 Published:2014-08-15
  • Contact: Chang Shan-Shan E-mail:whu.css1108@gmail.com
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 41204120 and 41304130) and the Fundamental Research Funds for the Central Universities (Grant No. 2042014kf0251).

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摘要： Modulated high frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low frequency (ELF)/very low frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high energy electrons. Combining the ray tracing method and test particle simulations, we evaluate the effects of energetic electron resonant scattering driven by the discrete, multi-frequency artificially generated ELF/VLF waves. The simulation results indicate a stochastic behavior of electrons and a linear profile of pitch angle and kinetic energy variations averaged over all test electrons. These features are similar to those associated with single-frequency waves. The computed local diffusion coefficients show that, although the momentum diffusion of relativistic electrons due to artificial ELF/VLF whistlers with a nominal amplitude of ～ 1 pT is minor, the pitch angle scattering can be notably efficient at low pitch angles near the loss cone, which supports the feasibility of artificial triggering of multi-frequency ELF/VLF whistler waves for the removal of high energy electrons from the magnetosphere. We also investigate the dependences of diffusion coefficients on the frequency interval (Δf) of the discrete, multi-frequency waves. We find that there is a threshold value of Δf for which the net diffusion coefficient of multi-frequency whistlers is inversely proportional to Δf (proportional to the frequency components Nw) when Δf is below the threshold value but it remains unchanged with increasing Δf when Δf is larger than the threshold value. This is explained as being due to the fact that the resonant scattering effect of broadband waves is the sum of the effects of each frequency in the 'effective frequency band'. Our results suggest that the modulation frequency of HF heating of the ionosphere can be appropriately selected with reasonable frequency intervals so that better performance of controlled precipitation of high energy electrons in the plasmasphere by artificial ELF/VLF whistler waves can be achieved.

关键词: wave-particle interactions, test particle simulations, discrete multi-frequency whistler waves, ionospheric modification

Abstract: Modulated high frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low frequency (ELF)/very low frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high energy electrons. Combining the ray tracing method and test particle simulations, we evaluate the effects of energetic electron resonant scattering driven by the discrete, multi-frequency artificially generated ELF/VLF waves. The simulation results indicate a stochastic behavior of electrons and a linear profile of pitch angle and kinetic energy variations averaged over all test electrons. These features are similar to those associated with single-frequency waves. The computed local diffusion coefficients show that, although the momentum diffusion of relativistic electrons due to artificial ELF/VLF whistlers with a nominal amplitude of ～ 1 pT is minor, the pitch angle scattering can be notably efficient at low pitch angles near the loss cone, which supports the feasibility of artificial triggering of multi-frequency ELF/VLF whistler waves for the removal of high energy electrons from the magnetosphere. We also investigate the dependences of diffusion coefficients on the frequency interval (Δf) of the discrete, multi-frequency waves. We find that there is a threshold value of Δf for which the net diffusion coefficient of multi-frequency whistlers is inversely proportional to Δf (proportional to the frequency components Nw) when Δf is below the threshold value but it remains unchanged with increasing Δf when Δf is larger than the threshold value. This is explained as being due to the fact that the resonant scattering effect of broadband waves is the sum of the effects of each frequency in the 'effective frequency band'. Our results suggest that the modulation frequency of HF heating of the ionosphere can be appropriately selected with reasonable frequency intervals so that better performance of controlled precipitation of high energy electrons in the plasmasphere by artificial ELF/VLF whistler waves can be achieved.

Key words: wave-particle interactions, test particle simulations, discrete multi-frequency whistler waves, ionospheric modification

中图分类号:  (Wave/particle interactions)

  • 94.20.wj
94.30.Ny (Energetic particle precipitation) 94.20.Vv (Ionospheric disturbances, irregularities, and storms) 94.30.Tz (Electromagnetic wave propagation)