| GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS |
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Evolution of Ring Current Protons Induced by Electromagnetic Ion Cyclotron Waves |
| XIAO Fu-Liang1,2, TIAN Tian3, CHEN Liang-Xu1, SU Zhen-Peng4, ZHENG Hui-Nan4 |
| 1School of Physics and Electronic Sciences, Changsha University of Science and Technology, Changsha 4100042State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 1001903School of Earth and Space Sciences, Peking University, Beijing 1008714CAS Key Lab for Basic Plasma Science, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 |
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| Cite this article: |
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XIAO Fu-Liang, TIAN Tian, CHEN Liang-Xu et al 2009 Chin. Phys. Lett. 26 119401 |
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Abstract We investigate the evolution of the phase space density (PSD) of ring current protons induced by electromagnetic ion cyclotron (EMIC) waves at the location L=3.5, calculate the diffusion coefficients in pitch angle and momentum, and solve the standard two-dimensional Fokker-Planck diffusion equation. The pitch angle diffusion coefficient is found to be larger than the momentum diffusion coefficient by a factor of about 103 or above at lower pitch angles. We show that EMIC waves can produce efficient pitch angle scattering of energetic (~100keV) protons, yielding a rapid decrement in PSD, typically by a factor of ~10 within a few hours, consistent with observational data. This result further supports previous findings that wave-particle interaction is responsible for the rapid ring current decay.
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| Keywords:
94.20.Wj
52.35.Hr
94.20.Ny
94.30.Xy
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Received: 07 April 2009
Published: 30 October 2009
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| PACS: |
94.20.wj
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(Wave/particle interactions)
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52.35.Hr
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(Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid))
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94.20.Ny
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94.30.Xy
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(Radiation belts)
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