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
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
摘要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.
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.
XIAO Fu-Liang;TIAN Tian;CHEN Liang-Xu;SU Zhen-Peng;ZHENG Hui-Nan. Evolution of Ring Current Protons Induced by Electromagnetic Ion Cyclotron Waves[J]. 中国物理快报, 2009, 26(11): 119401-119401.
XIAO Fu-Liang, TIAN Tian, CHEN Liang-Xu, SU Zhen-Peng, ZHENG Hui-Nan. Evolution of Ring Current Protons Induced by Electromagnetic Ion Cyclotron Waves. Chin. Phys. Lett., 2009, 26(11): 119401-119401.
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2009, Vol. 26 
