Global Occurrence of Higher-Bands ECH Waves in Radiation Belts Based on a Novel Noise Reduction Algorithm (NORA)

Abstract

Electrostatic electron cyclotron harmonic (ECH) waves which can efficiently produce scattering loss of electrons, are frequently observed in the first band. Here we present new results on the global occurrence of higher-band ECH waves in the radiation belts from Van Allen Probes data. We develop a novel noise reduction algorithm which can be widely applied to various plasma waves to better identify naturally occurring waves during periods of instrument interference. The occurrence rate of ECH waves in higher harmonic bands is comparable to that in the first harmonic band, except in the noon-to-dusk sector. As the level of geomagnetic activity increases, ECH waves in all bands can be observed at lower L-shells. The occurrence rates of weak (moderate, strong) waves in all four bands increase 3–4 (4–6, 5–10) times during disturbed periods compared to those during quiet periods. The current results may provide better understanding of ECH-driven magnetosphere-ionosphere coupling.