Zhu H., Z. Su, F. Xiao, H. Zheng, C. Shen, Y. Wang, S. Wang, (2012), Nonlinear interaction between ring current protons and electromagnetic ion cyclotron waves, J. Geophys. Res. [Space Physics], 117, doi:10.1029/2012JA018088

## Abstract

Electromagnetic ion cyclotron (EMIC) waves have long been suggested to account for the rapid decay of ring current, which is usually described by the quasi-linear theory. We demonstrate that the interactions between ring current protons and typical EMIC waves can be highly nonlinear. A dimensionless parameterRis derived to identify the nonlinear interaction region, and a test-particle simulation is performed to analyze the motions of typical (kinetic energyEk = 50 keV) ring current protons in detail. Nonlinear phase bunching occurs widely in the region R ∼1, whereas nonlinear phase trapping is confined in the region R∼ 1. The former produces the non-stochastic pitch angle decrease, probably increasing the overall loss rate predicted by the quasi-linear theory. In contrast, the latter causes the significant pitch angle increase, probably reducing the overall loss rate estimated from the quasi-linear theory. These two nonlinear mechanisms lead to complex advection and diffusion processes, and an advection-diffusion modeling is required to more accurately simulate the ring current decay induced by EMIC waves.## Authors (sorted by name)

Shen Su Xiao Zheng Zhu## Journal / Conference

Journal Of Geophysical Research (Space Physics)## Acknowledgments

This work was supported by the National Natural Science Foundation of China grants 41174125, 41131065, 41121003 and 41074120, the Chinese Academy of Sciences grant KZCX2‐EW‐QN510 and KZZD‐EW‐01‐4, the National Key Basic Research Special Foundation of China Grant 2011CB811403, and the Fundamental Research Funds for the Central Universities WK2080000031.## Bibtex

@article{doi:10.1029/2012JA018088,
author = {Zhu, Hui and Su, Zhenpeng and Xiao, Fuliang and Zheng, Huinan and Shen, Chao and Wang, Yuming and Wang, Shui},
title = {Nonlinear interaction between ring current protons and electromagnetic ion cyclotron waves},
journal = {Journal of Geophysical Research: Space Physics},
volume = {117},
number = {A12},
year = {2012},
pages = {},
keywords = {EMIC wave, phase bunching, phase trapping, ring current, wave-particle interaction},
doi = {10.1029/2012JA018088},
url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2012JA018088},
eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2012JA018088},
abstract = {Electromagnetic ion cyclotron (EMIC) waves have long been suggested to account for the rapid decay of ring current, which is usually described by the quasi-linear theory. We demonstrate that the interactions between ring current protons and typical EMIC waves can be highly nonlinear. A dimensionless parameterRis derived to identify the nonlinear interaction region, and a test-particle simulation is performed to analyze the motions of typical (kinetic energyEk = 50 keV) ring current protons in detail. Nonlinear phase bunching occurs widely in the region R ∼1, whereas nonlinear phase trapping is confined in the region R∼ 1. The former produces the non-stochastic pitch angle decrease, probably increasing the overall loss rate predicted by the quasi-linear theory. In contrast, the latter causes the significant pitch angle increase, probably reducing the overall loss rate estimated from the quasi-linear theory. These two nonlinear mechanisms lead to complex advection and diffusion processes, and an advection-diffusion modeling is required to more accurately simulate the ring current decay induced by EMIC waves.}
}