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Hot Plasma Effects on the Cyclotron‐Resonant Pitch‐Angle Scattering Rates of Radiation Belt Electrons Due to EMIC Waves
Author(s) -
Ni Binbin,
Cao Xing,
Shprits Yuri Y.,
Summers Danny,
Gu Xudong,
Fu Song,
Lou Yuequn
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl076028
Subject(s) - pitch angle , physics , dispersion relation , electron , scattering , atomic physics , emic and etic , cyclotron , van allen radiation belt , plasma , computational physics , optics , nuclear physics , geophysics , magnetosphere , sociology , anthropology
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 >5 MeV electrons. The most crucial differences introduced by the hot plasma effects occur for >3 MeV 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.