A “Trap‐Release‐Amplify” Model of Chorus Waves

Tao, X.; Zonca, F.; Chen, Liu

doi:10.1029/2021ja029585

Cited by 50 publications

(78 citation statements)

References 65 publications

(209 reference statements)

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“…Note that the dependence of Γ on L, predicted by Helliwell (1967) or Tao et al. (2021), is mainly a result of the “consistent‐wave” or the phase‐locking condition assumed by the models, which mean that the Doppler shifted wave frequency (

ω - k_{∥} v_{∥}

) matches the spatial variation of background magnetic field inhomogeneity. If, in case of very oblique propagation, the resonance condition responsible for falling‐tone chorus generation changes to

ω - k_{∥} v_{∥} = n {normalΩ}_{normale}

with n different from 1, then clearly Equation (14) of Helliwell, 1967 might not be applicable.…”

Section: Resultsmentioning

confidence: 94%

“…The oblique propagation could clearly affect the dependence of Γ on L through both cross field line propagation and the generation process. Note that the dependence of Γ on L, predicted by Helliwell (1967) or Tao et al (2021), is mainly a result of the "consistent-wave" or the phase-locking condition assumed by the models, which mean that the Doppler shifted wave frequency (     E k v ) matches the spatial variation of background magnetic field inhomogeneity. If, in case of very oblique propagation, the resonance condition responsible for falling-tone chorus generation changes to…”

Section: The Dependence Of τ and γ On L-shellmentioning

confidence: 97%

“…The generation mechanism of chorus responsible for frequency chirping and the potential effects of nonlinear wave‐particle interactions on radiation belt electron acceleration are important research topics (Helliwell, 1967; Nunn, 1974; Vomvoridis et al., 1982; Omura et al., 2008; Tao, Bortnik, et al., 2012, 2013, 2017, 2020, 2021; Artemyev et al., 2016, 2021; Zhang, Agapitov, et al., 2020, 2021; Demekhov, 2011; Demekhov et al., 2006; Nunn et al., 2005; Trakhtengerts, 1995) Relevant to both topics are the detailed properties of chorus elements, such as duration, frequency chirping rate, and the period of repetition. The detailed characteristics of rising‐tone chorus elements have been investigated by several studies.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Xie

Teng

et al. 2021

Geophysical Research Letters

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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.

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ω - k_{∥} v_{∥}

ω - k_{∥} v_{∥} = n {normalΩ}_{normale}

with n different from 1, then clearly Equation (14) of Helliwell, 1967 might not be applicable.…”

Section: Resultsmentioning

confidence: 94%

Section: The Dependence Of τ and γ On L-shellmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Xie

Teng

et al. 2021

Geophysical Research Letters

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“…This assumption of S = 0 at the equator simplifies the model description of the trapped electron dynamics. Although in more realistic simulations with a finite size of the wave generation region [65][66][67][68][69][70] trapped electrons may cross the equator without detrapping, in general this effect should not significantly alter the trapped electron energy and pitch-angle changes.…”

Section: Field-aligned Whistler-mode Wavesmentioning

confidence: 99%

Transitional regime of electron resonant interaction with whistler-mode waves in inhomogeneous space plasma

et al. 2021

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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“…Helliwell (1967) proposed that the frequency sweep rates are determined by the nonuniform ambient magnetic field. More recently, Tao et al (2021) refined Helliwell's model as the Trap-Release-Amplify (TaRA) model, in which the frequency sweep rate at the initial phase of chorus emissions is determined by the gradient of the background magnetic field. Since our recent particle simulations (Nogi et al, 2020) show results different from the TaRA model, it is still necessary to study the generation process of chorus emissions quantitatively by simulations to clarify the difference between these models and identify the essential physics of chorus wave generation.…”

Section: 1029/2021ja029826mentioning

confidence: 99%

Nonlinear Signatures of VLF‐Triggered Emissions: A Simulation Study

Nogi

Omura

2021

JGR Space Physics

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Whistler-mode chorus emissions with rising-tone and falling-tone frequencies have been studied for more than half a century. Chorus emissions are often observed outside the plasmapause in conjunction with magnetospheric substorms (Tsurutani & Smith, 1974). Chorus emissions are essentially nonlinear phenomena induced by finite amplitude waves as evidenced by the triggered emissions from the VLF transmitters, which exhibit the same frequency spectra with varying frequencies (see a review by Omura et al., 1991;Gołkowski et al., 2019). Recently, demonstration and science experiments (DSX;Scherbarth et al., 2009) was conducted for the study of whistler-mode wave-particle interactions. They injected whistler-mode wave to trigger new emissions in the magnetosphere. Propagation characteristics of the DSX waves have been studied base on ray-tracing (Reid et al., 2021). Chorus is an emission triggered by a naturally growing wave at a fixed frequency as predicted by linear growth rates (Kennel & Petschek, 1966). From the electromagnetic thermal fluctuations, a wave with the maximum linear growth rate grows to the largest amplitude, and it suppresses growth of other waves with frequencies close to its frequency through scattering of resonant electrons. The wave becomes coherent and works as a triggering wave we assume in the present study. Under a finite amplitude coherent wave, resonant electrons undergo nonlinear motion and form either an electron hole or a hill, inducing resonant currents. The resonant currents cause variation of the wave amplitude and frequency as described by the wave equations (Nunn, 1974;Omura et al., 1991Omura et al., , 2008Vomvoridis et al., 1982). A wave with a frequency different from that of the triggering wave is generated as a wave packet independent from the triggering wave. The evolution of the newly generated wave packet has not been understood completely. It has been reported that series of short wave packets are generated sequentially, forming rising and/or falling-tone emissions. Each wave packet is called a subpacket of chorus elements (Foster et al., 2017;Santolík et al., 2014). Subpacket structures of chorus waves have great importance on electron acceleration and pitch angle scattering.A simulation study has shown that efficient electron acceleration takes place by a finite packet via nonlinear electron trapping (Hiraga & Omura, 2020). Electron precipitations to the ionosphere due to chorus waves are observed by simultaneous observations between satellite and ground, which show the agreement with the pulsating aurora and each of chorus emissions with subpacket structure (Kasahara et al., 2018;Ozaki et al., 2018). A particle simulation of triggered emission (Hikishima et al., 2010) also showed that each triggered chorus element has subpacket structure and the electron flux is strongly modulated by the subpackets.The subpacket structure is also found in electromagnetic ion cyclotron (EMIC) rising-tone emissions (Nakamura et al., 2014). A model of the generation process of EMIC emissions...

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A “Trap‐Release‐Amplify” Model of Chorus Waves

Cited by 50 publications

References 65 publications

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

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

Transitional regime of electron resonant interaction with whistler-mode waves in inhomogeneous space plasma

Nonlinear Signatures of VLF‐Triggered Emissions: A Simulation Study

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