TY  - JOUR
A1  - Cao, Xing
A1  - Ni, Binbin
A1  - Summers, Danny
A1  - Shprits, Yuri Y.
A1  - Gu, Xudong
A1  - Fu, Song
A1  - Lou, Yuequn
A1  - Zhang, Yang
A1  - Ma, Xin
A1  - Zhang, Wenxun
A1  - Huang, He
A1  - Yi, Juan
T1  - Sensitivity of EMIC wave-driven scattering loss of ring current protons to wave normal angle distribution
JF  - Geophysical research letters
N2  - Electromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field-aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of <= 10 keV protons. For >10 keV protons, the field-aligned propagation approximation results in a pronounced underestimate of the scattering of intermediate equatorial pitch angle protons and overestimates the scattering of high equatorial pitch angle protons by orders of magnitude. Our results suggest that the wave normal distribution of electromagnetic ion cyclotron waves plays an important role in the pitch angle evolution and scattering loss of ring current protons and should be incorporated in future global modeling of ring current dynamics.
Y1  - 2019
U6  - https://doi.org/10.1029/2018GL081550
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 2
SP  - 590
EP  - 598
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ni, Binbin
A1  - Cao, Xing
A1  - Shprits, Yuri Y.
A1  - Summers, Danny
A1  - Gu, Xudong
A1  - Fu, Song
A1  - Lou, Yuequn
T1  - Hot Plasma Effects on the Cyclotron-Resonant Pitch-Angle Scattering Rates of Radiation Belt Electrons Due to EMIC Waves
JF  - Geophysical research letters
N2  - To investigate the hot plasma effects on the cyclotron-resonant interactions between electromagnetic ion cyclotron (EMIC) waves and radiation belt electrons in a realistic magnetospheric environment, calculations of the wave-induced bounce-averaged pitch angle diffusion coefficients are performed using both the cold and hot plasma dispersion relations. The results demonstrate that the hot plasma effects have a pronounced influence on the electron pitch angle scattering rates due to all three EMIC emission bands (H+, He+, and O+) when the hot plasma dispersion relation deviates significantly from the cold plasma approximation. For a given wave spectrum, the modification of the dispersion relation by hot anisotropic protons can strongly increase the minimum resonant energy for electrons interacting with O+ band EMIC waves, while the minimum resonant energies for H+ and He+ bands are not greatly affected. For H+ band EMIC waves, inclusion of hot protons tends to weaken the pitch angle scattering efficiency of >5MeV electrons. The most crucial differences introduced by the hot plasma effects occur for >3MeV electron scattering rates by He+ band EMIC waves. Mainly due to the changes of resonant frequency and wave group velocity when the hot protons are included, the difference in scattering rates can be up to an order of magnitude, showing a strong dependence on both electron energy and equatorial pitch angle. Our study confirms the importance of including hot plasma effects in modeling the scattering of ultra-relativistic radiation belt electrons by EMIC waves.
Y1  - 2018
U6  - https://doi.org/10.1002/2017GL076028
SN  - 0094-8276
SN  - 1944-8007
VL  - 45
IS  - 1
SP  - 21
EP  - 30
PB  - American Geophysical Union
CY  - Washington
ER  -