Statistical Analysis of Electromagnetic Ion Cyclotron Rising‐Tone Emissions Based on Deep Learning

Wang, Yan; Li, Yilong; Liu, Kaijun; Song, Weibin; Xiong, Ying; Yao, Fei

doi:10.1029/2022ja031085

Cited by 2 publications

(2 citation statements)

References 43 publications

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“…Another factor that should be accounted for in the real magnetosphere is the potential nonlinear effect on the HFEMIC wave growth. Magnetospheric chorus-like risingtone EMIC waves are often observed in the inner magnetosphere (Grison et al, 2013(Grison et al, , 2018Nakamura et al, 2014Nakamura et al, , 2016Pickett et al, 2010;Wang et al, 2023) which are attributed to a nonlinear process involving phase trapping and phase bunching (Omura et al, 2010;Shoji et al, 2017Shoji et al, , 2021Shoji & Omura, 2013). Nonlinear theory predicts a much larger growth rate, and this may explain HFEMIC wave growth despite the narrow source region.…”

Section: Introductionmentioning

confidence: 99%

Linear Theory Analysis and One‐Dimensional Hybrid Simulations of High‐Frequency EMIC Waves in a Dipole Magnetic Field

Min

2024

JGR Space Physics

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Narrowband (Δf ≲ 0.1fcp), high‐frequency (0.9fcp ≲ f < fcp) electromagnetic ion cyclotron (EMIC) waves, or HFEMIC waves for short, are a relatively new type of EMIC waves, where fcp is the proton cyclotron frequency. Here, we investigate the instability threshold conditions and the nonlinear evolution of HFEMIC waves at parallel propagation. First, linear theory analysis is extended to a regime relevant to HFEMIC waves (parallel proton beta β‖p < 0.01). The instability threshold follows a similar anisotropy‐β‖p relation and requires a large value of anisotropy (T⊥p/T‖p ≳ 10) for wave growth. As a result of decreasing group velocity, the convective growth rate at a fixed threshold exhibits a similar inverse relation with β‖p. Heavy ions affect the instability only weakly, primarily through the introduction of stop bands. Second, we carry out one‐dimensional hybrid simulations in a parabolic background magnetic field, with initial parameters constrained by observation. Despite the narrow source region (within about ±3° latitude), HFEMIC waves can grow well above the thermal noise level due in large part to a small group velocity of HFEMIC waves. The saturation level is well within the range of observational amplitudes, and the quasilinear process primarily determines the wave evolution. Finally, we demonstrate that the present results compare favorably to the recent statistical results, thereby supporting anisotropic low‐energy protons as free energy source for HFEMIC waves.

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Section: Introductionmentioning

confidence: 99%

Linear Theory Analysis and One‐Dimensional Hybrid Simulations of High‐Frequency EMIC Waves in a Dipole Magnetic Field

Min

2024

JGR Space Physics

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“…While there are several observational studies about EMIC wave chirping (Grison et al., 2013; Mursula, 2007; Mursula et al., 1994; Nakamura et al., 2016; Pickett et al., 2010; Y. Wang et al., 2023), theoretical studies are quite limited. Hybrid simulations have clearly demonstrated that EMIC wave frequency chirping is caused by nonlinear processes (Shoji & Omura, 2013).…”

Section: Introductionmentioning

confidence: 99%

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

An,

Tao,

Zonca

et al. 2024

Geophysical Research Letters

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Electromagnetic ion cyclotron (EMIC) waves are known to exhibit frequency chirping occasionally, contributing to the rapid acceleration and precipitation of energetic particles in the magnetosphere. However, the chirping mechanism of EMIC waves remains elusive. In this work, a phenomenological model of whistler mode chorus waves named the Trap‐Release‐Amplify (TaRA) model is applied to EMIC waves. Based on the proposed model, we explain how the chirping of EMIC waves occurs, and give predictions on their frequency chirping rates. For the first time, we relate the frequency chirping rate of EMIC waves to both the wave amplitude and the background magnetic field inhomogeneity. Direct observational evidence is provided to validate the model using previously published events of chirping EMIC waves. Our results not only provide a new model for EMIC wave frequency chirping, but more importantly, they indicate the potential wide applicability of the underlying principles of TaRA model.

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Statistical Analysis of Electromagnetic Ion Cyclotron Rising‐Tone Emissions Based on Deep Learning

Abstract: Electromagnetic ion cyclotron (EMIC) waves with fine rising-tone spectral structures have been observed by

Cited by 2 publications

References 43 publications

Linear Theory Analysis and One‐Dimensional Hybrid Simulations of High‐Frequency EMIC Waves in a Dipole Magnetic Field

Linear Theory Analysis and One‐Dimensional Hybrid Simulations of High‐Frequency EMIC Waves in a Dipole Magnetic Field

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

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