Global morphology and spectral properties of EMIC waves derived from CRRES observations

Abstract Gyroresonant wave‐particle interactions with electromagnetic ion cyclotron (EMIC) waves are a potentially important loss process for relativistic electrons in the Earth's radiation belts. Here we perform a statistical analysis of the EMIC waves observed by the Combined Release and Radiation Effects Satellite (CRRES) to determine the global morphology and spectral properties of the waves and to help assess their role in radiation belt dynamics. Helium band EMIC waves, with intensities, , greater than 0.1 nT 2 , are most prevalent during active conditions ( A E > 300 nT), from 4 < L * < 7 in the afternoon sector, with an average percentage occurrence of 2.7%. Hydrogen band EMIC wave events, with intensities greater than 0.1 nT 2 , are also most prevalent in the afternoon sector during active conditions in the same region, but they are less frequent with an average percentage occurrence of 0.6%. The average intensity of the helium and hydrogen band EMIC waves in the region 4 < L * < 7 in the afternoon sector during active conditions is 2 nT 2 and 0.5 nT 2 , respectively, and suggests that the waves can cause strong diffusion. However, the time‐averaged properties are very different, being a factor of 30–50 lower for helium and hydrogen band EMIC waves, respectively, suggesting that the overall effect will be correspondingly weaker. Nevertheless, the moderate and strong EMIC wave events with reported on here will contribute to relativistic electron loss in the Earth's radiation belts and should be included in radiation belt models.