Abstract Electromagnetic ion cyclotron (EMIC) waves are a key driver of particle precipitation and energy redistribution in the magnetosphere. While they have been extensively studied in the inner magnetosphere, their behavior in the outer magnetosphere remains poorly understood. In this study, we utilize ground‐based measurements from the Autonomous Adaptive Low‐Power Instrument Platform (AAL‐PIP) chain to investigate the occurrence and amplitude of H‐band and He‐band EMIC waves under varying AE, SYM‐H, and solar wind dynamic pressure () in Earth's outer magnetosphere ( L > 7). In the outer magnetosphere, both the occurrence rate and amplitude of EMIC waves increase under high AE and enhanced conditions, similar to responses in the inner magnetosphere. However, unlike the inner magnetosphere, where EMIC waves are generally confined near noon, enhanced in the outer magnetosphere drives waves across a broader magnetic local time (MLT) distribution, including the dawn and dusk sectors. Furthermore, during substorm periods, H‐band EMIC waves are absent in the dawn sector—a feature rarely observed in the inner region. SYM‐H shows only a weak correlation with wave amplitude and He‐band wave occurrence, while a stronger correlation is found with H‐band wave activity in both dawn and dusk sectors. Additionally, the radial dependencies also differ: as L increases, the wave occurrence rate decreases for both bands, but H‐band amplitudes increase while He‐band amplitudes decrease. This likely reflects differences in ion composition and wave growth conditions at larger radial distances. This study provides new insights into the global distribution and driving physics of EMIC wave activity in the outer magnetosphere.
Shao et al. (Thu,) studied this question.
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