Uncovering the Generation Mechanism of Low‐Frequency Chorus Waves (<0.1 fce_eq) During Active Geomagnetic Environments

Abstract Low‐frequency chorus waves (below 0.1 , where is equatorial electron gyrofrequency) can induce the depletion of relativistic electrons in Earth's radiation belts by effective pitch angle scattering, demonstrating distinct effects on radiation belt dynamics compared to typical chorus waves (0.1–0.8 ). However, their generation mechanism and environmental drivers remain poorly understood. Analysis of Van Allen Probes data reveals that low‐frequency chorus waves predominantly occur in the region of MLT range of 0–7 hr and L ∼ 6. These waves show a strong correlation with intense substorm activity and moderate magnetic storms, with the majority of waves clustering during storm‐time substorms. Their excitation mechanism is driven by the coexistence of isotropic low‐energy electrons (below 30 keV) and anisotropic high‐energy electrons (above 50 keV) during the storm's peak, along with concurrent geomagnetic field weakening due to enhanced ring currents.