Concurrent Observation of High‐Frequency EMIC Waves and Low‐Harmonic MS Waves Within a Magnetic Dip in the Inner Magnetosphere

Abstract

AbstractElectromagnetic ion cyclotron (EMIC) waves and fast magnetosonic (MS) waves were previously reported to be simultaneously generated by ring current protons (10s keV) within the magnetic dip. In this work, we present a distinct physical scenario of concurrent high‐frequency EMIC (HFEMIC) and MS waves within a magnetic dip where low‐energy (10s–100s eV) and hot (10s keV) protons facilitate the local growth of HFEMIC and MS waves, respectively. Moreover, the low‐energy protons exhibit remarkable perpendicular flux enhancements, which are well modulated by MS waves as evidenced by their significant correlation coefficient (∼0.78). Consequently, the concurrent two wave modes should arise from the complicated coupling between HFEMIC and MS waves, marking a departure from previous studies. Our observations demonstrate that the magnetic dip can provide favorable conditions for such intricate coupling processes, offering novel insights into its impact on magnetospheric dynamics.