A model for falling-tone chorus

Soto-chavez, A. R.; Wang, G.; Bhattacharjee, A.; Fu, G. Y.; Smith, H. M.

doi:10.1002/2014gl059320

Cited by 23 publications

(23 citation statements)

References 24 publications

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“…While the non-linear theory of parallel chorus wave growth is now well-established (e.g., see Trakhtengerts et al 2004;Demekhov 2011;Katoh and Omura 2011;Katoh 2014), the generation of quasi-electrostatic lowerband chorus waves with both rising and falling tones still remains largely unexplainedalthough a few preliminary models have recently been proposed for falling tones (Nunn and Omura 2012;Yamaguchi et al 2013;Soto-Chavez et al 2014;Nunn and Omura 2015). Here below, we discuss a simplified model of oblique wave generation and derive the corresponding frequency sweep rate ∂ω/∂t.…”

Section: Frequency Sweep Ratesmentioning

confidence: 99%

Oblique Whistler-Mode Waves in the Earth’s Inner Magnetosphere: Energy Distribution, Origins, and Role in Radiation Belt Dynamics

et al. 2016

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International audienceIn this paper we review recent spacecraft observations of oblique whistler-mode waves in the Earth’s inner magnetosphere as well as the various consequences of the presence of such waves for electron scattering and acceleration. In particular, we survey the statistics of occurrences and intensity of oblique chorus waves in the region of the outer radiation belt, comprised between the plasmapause and geostationary orbit, and discuss how their actual distribution may be explained by a combination of linear and non-linear generation, propagation, and damping processes. We further examine how such oblique wave populations can be included into both quasi-linear diffusion models and fully nonlinear models of wave-particle interaction. On this basis, we demonstrate that varying amounts of oblique waves can significantly change the rates of particle scattering, acceleration, and precipitation into the atmosphere during quiet times as well as in the course of a storm. Finally, we discuss possible generation mechanisms for such oblique waves in the radiation belts. We demonstrate that oblique whistler-mode chorus waves can be considered as an important ingredient of the radiation belt system and can play a key role in many aspects of wave-particle resonant interactions

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Section: Frequency Sweep Ratesmentioning

confidence: 99%

Oblique Whistler-Mode Waves in the Earth’s Inner Magnetosphere: Energy Distribution, Origins, and Role in Radiation Belt Dynamics

et al. 2016

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“…Both, for quasi‐linear [ Shprits et al , ; Summers et al , ] and nonlinear [ Nunn , ; Trakhtengerts et al , ; Omura et al , ; Nunn et al , ] interaction models, it is usually assumed that chorus propagates at wave normal angles almost parallel to the ambient magnetic field direction. Only a few models allow for oblique propagation [ Bell , ; Albert , ; Shklyar and Matsumoto , ; Nunn et al , ; Soto‐Chavez et al , ], but these models have not been developed sufficiently enough to yield a complete picture. It is not uncommon to observe high wave normal angles for chorus close to the equator, especially for the falling tones [ Cornilleau‐Wehrlin et al , ; Santolík et al , ; Li et al , ; Agapitov et al , ].…”

Section: Introductionmentioning

confidence: 99%

Wave normal angles of whistler mode chorus rising and falling tones

et al. 2014

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We present a study of wave normal angles (θk) of whistler mode chorus emission as observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) during the year 2008. The three inner THEMIS satellites THA, THD, and THE usually orbit Earth close to the dipole magnetic equator (±20°), covering a large range of L shells from the plasmasphere out to the magnetopause. Waveform measurements of electric and magnetic fields enable a detailed polarization analysis of chorus below 4 kHz. When displayed in a frequency‐θk histogram, four characteristic regions of occurrence are evident. They are separated by gaps at f/fc,e≈0.5 (f is the chorus frequency, fc,e is the local electron cyclotron frequency) and at θk∼40°. Below θk∼40°, the average value for θk is predominantly field aligned, but slightly increasing with frequency toward half of fc,e (θk up to 20°). Above half of fc,e, the average θk is again decreasing with frequency. Above θk∼40°, wave normal angles are usually close to the resonance cone angle. Furthermore, we present a detailed comparison of electric and magnetic fields of chorus rising and falling tones. Falling tones exhibit peaks in occurrence solely for θk>40° and are propagating close to the resonance cone angle. Nevertheless, when comparing rising tones to falling tones at θk>40°, the ratio of magnetic to electric field shows no significant differences. Thus, we conclude that falling tones are generated under similar conditions as rising tones, with common source regions close to the magnetic equatorial plane.

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“…Theoretically, it is widely accepted that chorus waves are generated nonlinearly (Helliwell, 1967;Vomvoridis et al, 1982;Omura et al, 2008;Tao et al, 2017a, b), although the detailed physical process is still an ongoing research topic. Most existing theories and particle-in-cell type simulations are 10 about rising tone chorus waves (Helliwell, 1965;Sudan and Ott, 1971;Nunn, 1974;Vomvoridis et al, 1982;Trakhtengerts, 1995;Omura et al, 2008;Tao, 2014); only a few theoretical models have been proposed for falling tone chorus (Nunn and Omura, 2012;Soto-Chavez et al, 2014;Mourenas et al, 2015). In this work, we consider rising tone and falling tone chorus waves separately.…”

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confidence: 99%

A statistical study of spatial distribution and source region size of chorus waves using Van Allen Probes data

Teng¹,

Tao²,

Li³

et al. 2018

Preprint

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Abstract. Spatial distribution and source region size of chorus waves are important parameters in understanding their generation. In this work, we analyze over 3 years of continuous wave burst mode data from Van Allen Probes and build a data set of rising and falling tone chorus. For the L shell range covered by Van Allen Probes data (3.5 ≤ L ≤ 7), statistical results demonstrate that the sector where rising tones are most likely to be observed is the dayside during geomagnetically quiet and moderate times and the dawnside during active times. Moreover, rising tone chorus waves have a higher occurrence rate near 5 the equatorial plane, while the falling tone chorus waves have a higher possibility to be observed at lower L-shell and higher magnetic latitude. By analyzing the direction of Poynting wave vector, we statistically investigate the chorus source region size along a field line, and compare the results with previous theoretical estimates. Our analysis confirms previous conclusions that both rising tone and falling tone chorus waves are generated near the equatorial plane, and shows that previous theoretical estimates roughly agree with the observation within a factor of two. Our results provide important insights into further 10 understanding of chorus generation.

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A model for falling-tone chorus

Cited by 23 publications

References 24 publications

Oblique Whistler-Mode Waves in the Earth’s Inner Magnetosphere: Energy Distribution, Origins, and Role in Radiation Belt Dynamics

Oblique Whistler-Mode Waves in the Earth’s Inner Magnetosphere: Energy Distribution, Origins, and Role in Radiation Belt Dynamics

Wave normal angles of whistler mode chorus rising and falling tones

A statistical study of spatial distribution and source region size of chorus waves using Van Allen Probes data

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