Statistical Study on Coherent Quasi‐Periodic Emissions Based on Multi‐Satellite Measurements

Quasi‐periodic (QP) emissions, a type of whistler‐mode electromagnetic waves with QP intensity modulation, play a significant role in magnetospheric electron dynamics through wave‐particle interactions. While previous studies have identified QP events via manual spectrogram inspection, here we present an automated detection method leveraging coherence analysis of simultaneous measurements from the China Seismo‐Electromagnetic Satellite and Van Allen Probes to systematically characterize coherent QP emissions. From October 2017 to July 2019, 224 coherent QP events were identified across conjugate satellite combinations. These events exhibit frequencies spanning from ∼500 to 2,600 Hz, with majority concentrated between 600 and 2,200 Hz, and modulation periods ranging from 10 to 220 s (median: 47 s). Equatorial distribution reveals a duskside (12–18 magnetic local times (MLT)) dominance in occurrence rates, consistent with plasmaspheric density asymmetries. The spatial extents of the majority QP emissions are predominantly ∼3.5 RE in radial direction and ∼2 MLT in azimuthal direction. Events with shorter modulation periods (≤47 s) extend more broadly, reaching maximum observed extents of 6 RE radially and 6 MLT azimuthally. Our results are of interest for studying the origin and propagation of the QP emission.