Drift‐Bounce Resonance Between Pc5 Pulsations and Ions at Multiple Energies in the Nightside Magnetosphere: Arase and MMS Observations

Abstract

Abstract A Pc5 wave is observed by the Exploration of energization and Radiation in Geospace Arase satellite in the inner magnetosphere ( L ~5.4–6.1) near postmidnight ( L ‐magnetic local time ~1.8–2.5 hr) during the storm recovery phase on 27 March 2017. Its azimuthal wave number ( m ‐number) is estimated using two independent methods with satellites and ground observations to be −8 to −15. The direct measurement of the m ‐number enables us to calculate the resonance energy. The flux oscillations of H + and O + ions at ≥ 56.3 keV are caused by drift resonance and those of O + ions at ≤ 18.6 keV by bounce resonance. Resonances of O + ions at multiple energies are simultaneously observed for the first time. The enhancement of the O + /H + flux ratio at ≤ 18.6 keV indicates selective acceleration of O + ions through bounce resonance.