A Statistical Analysis of Duration and Frequency Chirping Rate of Falling Tone Chorus

Abstract

The duration (τ) and chirping rate (Γ) of whistler mode chorus waves are two of the most important properties to understand chorus generation mechanism and to quantify effects of nonlinear wave particle interactions on radiation belt electron acceleration. In this study, we perform the first statistical analysis of the duration and chirping rate of falling tone chorus elements using Van Allen Probes data. We found that τ increases and Γ decreases with increasing L‐shell, although the dependence is weak. The duration from dawnside and dayside have similar distributions, which is a bit longer than those from duskside and nightside. However, Γ has little dependence on MLT. The relation between τ and Γ shows that τ scales with Γ as τ∼normalΓ−0.64, supporting one of the previous theoretical models of rising tone chorus in Teng et al. (2017). Our results should provide important insights to deepen our understanding of falling tone chorus excitation.

Frequency Chirping of Electromagnetic Ion Cyclotron Waves in Earth's Magnetosphere

“…Correspondingly, the direct comparison presented in Figure 3 demonstrates very good agreement between the new model and previously published observations. Furthermore, similar to chorus waves (Tao, Li, et al., 2012; Tao et al., 2014; Xie et al., 2021), we can see a decrease of chirping rate as L increases because of smaller magnetic field inhomogeneity at larger L ‐shells.…”

Influence of Solar Wind Dynamic Pressure on Distribution of Whistler Mode Waves Based on Van Allen Probe Observations

“…Previous study indicates that the inhomogeneity of the background magnetic field has effect on the generation process of whistler-mode chorus emissions. The small spatial inhomogeneity of the background magnetic field leads to the small threshold amplitude of nonlinear wave growth, and allows the triggering process of rising tone elements to easily occur in the equatorial region of the magnetosphere (Katoh and Omura., 2013;Teng et al, 2018aTeng et al, , 2018bTeng & Tao, 2022;Wu et al, 2020;Xie et al, 2021).…”

Propagation of Very Oblique Chorus Waves Near a Plasmaspheric Plume Boundary

“…The emissions are observed in the plasma trough, at all local times but predominantly from the post‐midnight to the morning sectors (Agapitov et al., 2018; Meredith et al., 2020). The frequency‐time spectrum of chorus emissions includes discrete rising tone or falling tone elements with durations of several 0.1 s (Teng et al., 2017; Xie et al., 2021). A frequency gap is usually present in the spectrum at half of the equatorial electron gyrofrequency and divides the spectrum into an upper band above the gap and a lower band below the gap (Tsurutani & Smith, 1974; Teng et al., 2019; J. Li et al., 2019).…”