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.

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We perform a detailed analysis of bounce‐resonant pitch angle scattering of radiation belt electrons due to electromagnetic ion cyclotron (EMIC) waves. It is found that EMIC waves can resonate with near‐equatorially mirroring electrons over a wide range of L shells and energies. H+ band EMIC waves efficiently scatter radiation belt electrons of energy >100 keV from near 90° pitch angles to lower pitch angles where the cyclotron resonance mechanism can take over to further diffuse electrons into the loss cone. Bounce‐resonant electron pitch angle scattering rates show a strong dependence on L shell, wave normal angle distribution, and wave spectral properties. We find distinct quantitative differences between EMIC wave‐induced bounce‐resonant and cyclotron‐resonant diffusion coefficients. Cyclotron‐resonant electron scattering by EMIC waves has been well studied and found to be a potentially crucial electron scattering mechanism. The new investigation here demonstrates that bounce‐resonant electron scattering may also be very important. We conclude that bounce resonance scattering by EMIC waves should be incorporated into future modeling efforts of radiation belt electron dynamics.

Based on the high‐resolution FFF wave spectral data obtained from the three innermost Time History of Events and Macroscale Interactions during Substorms spacecraft, electrostatic electron cyclotron harmonic (ECH) emissions are identified, using automatic selection criteria, for the period from May 2010 to December 2015. A statistical analysis of wave spectral intensity, peak wave frequency, and wave occurrence rate is performed for the first harmonic ECH waves that are predominantly strongest among all harmonic bands, in terms of dependence on L shell, magnetic local time (MLT), magnetic latitude, and the level of geomagnetic activity. Our results indicate that ECH emissions are preferentially a nightside phenomenon primarily confined to the MLT interval of 21–06 and that the most intense ECH waves are commonly present at L = 5–9 and MLT = 23–03 within 3° of the magnetic equator. As the geomagnetic activity intensifies, averaged nightside ECH wave amplitude can increase from a few tenth mV/m to well above 1 mV/m. The presence of >0.1 mV/m ECH emissions extends from L < 10 to L > ~12 with a broad MLT coverage from the evening to postdawnside at the occurrence rate above 20% for the equatorial emissions and at a rate up to ~7% for higher‐latitude waves. Overall, the average peak wave frequency of the first harmonic ECH waves is located ~1.5 fce (where fce is the electron gyrofrequency) for L < 10 and becomes smaller at higher L shells. It also exhibits a tendency to shift to lower frequencies with increasing geomagnetic activity level. By finalizing a numeric table that gives the statistically average values of wave amplitude and peak wave frequency for different ranges of L shell, MLT, and geomagnetic activity level, our detailed investigation provides an improved statistical model of ECH wave global distribution in the Earth's inner and outer magnetosphere, which can be readily adopted as critical inputs in diffusion codes to evaluate the rates of ECH wave‐driven pitch angle scattering and to determine the precise contributions of ECH waves to the plasma sheet electron dynamics and diffuse auroral electron precipitation.