Nonlinear Wave Growth Analysis of Chorus Emissions Modulated by ULF Waves

Li, Li; Omura, Yoshiharu; Zhou, X.‐Z.; Zong, Qiugang; Rankin, R.; Yue, Chao; Fu, S. Y.

doi:10.1029/2022gl097978

Cited by 18 publications

(37 citation statements)

References 93 publications

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Section: Event #1supporting

confidence: 92%

“…There is a reasonably good correlation of whistler wave bursts and local δB ‖ minima (see expanded view of Panel (e) in Panel (g)). These observations are consistent with a scenario of a ULF‐wave modulated thermal electron anisotropy, resulting in the observed quasi‐periodic generation of whistler waves (as previously reported by W. Li, Bortnik, et al., 2011; L. Li et al., 2022; Xia et al., 2020; Zhang et al., 2019). Note the adiabatic effect of ULF waves (i.e., betatron heating/cooling) on electron distributions would reduce the electron anisotropy around the local plasma density enhancements (magnetic field minima), and thus will not generate strong whistler‐mode waves (see discussion in Watt et al., 2011).…”

Section: Analysis Of Selected Eventssupporting

confidence: 92%

“…A classical example of dynamic precipitation is the pulsating aurora (Belon et al., 1969; Coroniti & Kennel, 1970; Johnstone, 1978; McEwen et al., 1981), which is associated with ∼10 keV electron precipitation as a result of quasi‐periodic whistler‐mode (chorus) wave scattering (Kasahara et al., 2018; Nishimura et al., 2010). The quasi‐periodicity of these wave emissions may be caused by usltra‐low‐frequency (ULF) waves modulating plasma and energetic electron fluxes around the equator (Bryant et al., 1971; Coroniti & Kennel, 1970; Jaynes, Lessard, et al., 2015; W. Li, Bortnik, et al., 2011; W. Li, Thorne, Bortnik, Nishimura, & Angelopoulos, 2011; L. Li et al., 2022; Motoba et al., 2013; Watt et al., 2011). Recent optical and low‐altitude measurements showed that ≲10 keV precipitation forming the pulsating aurora may be accompanied by precipitation of relativistic electrons (Miyoshi et al., 2020; Shumko et al., 2021), which makes such a quasi‐periodic precipitation pattern particularly important in the context of energetic electron losses and altering of atmosphere properties (Miyoshi et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

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On the Role of ULF Waves in the Spatial and Temporal Periodicity of Energetic Electron Precipitation

et al. 2022

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Section: Event #1supporting

confidence: 92%

Section: Analysis Of Selected Eventssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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On the Role of ULF Waves in the Spatial and Temporal Periodicity of Energetic Electron Precipitation

et al. 2022

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“…This is likely an effect of precipitation modulation by ULF waves (Motoba et al., 2013). Such waves preferentially originate from the dawn flank magnetopause due to foreshock transients (Hartinger et al., 2013, 2014), propagate to lower L (Klimushkin et al., 2019; Wright & Elsden, 2020; X. J. Zhang, Angelopoulos, et al., 2020), and modulate the equatorial generation of whistler‐mode chorus waves (W. Li, Thorne, Bortnik, Nishimura, & Angelopoulos, 2011; L. Li et al., 2022; Watt et al., 2011; Xia et al., 2016; X.‐J. Zhang et al., 2019) responsible for electron precipitation.…”

Section: Elfin Observationsmentioning

confidence: 99%

“…(2016); L. Li et al. (2022)). Accordingly, we anticipate observations of a stable electron precipitation pattern at ELFIN on a spatial scale of a few to a few tens of seconds, and with similar profiles and intensity on consecutive passes separated by less than 30 s. However such profiles of precipitating fluxes should vary (potentially in absolute intensity, location or extent) temporally (from one crossing to the next), in events as the inter‐satellite separation increases from 0.5 min to a few minutes.…”

Section: Introductionmentioning

confidence: 99%

Temporal Scales of Electron Precipitation Driven by Whistler‐Mode Waves

et al. 2023

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Electron resonant scattering by whistler‐mode waves is one of the most important mechanisms responsible for electron precipitation to the Earth's atmosphere. The temporal and spatial scales of such precipitation are dictated by properties of their wave source and background plasma characteristics, which control the efficiency of electron resonant scattering. We investigate these scales with measurements from the two low‐altitude Electron Losses and Fields Investigation (ELFIN) CubeSats that move practically along the same orbit, with along‐track separations ranging from seconds to tens of minutes. Conjunctions with the equatorial THEMIS mission are also used to aid our interpretation. We compare the variations in energetic electron precipitation at the same L‐shells but on successive data collection orbit tracks by the two ELFIN satellites. Variations seen at the smallest inter‐satellite separations, those of less than a few seconds, are likely associated with whistler‐mode chorus elements or with the scale of chorus wave packets (0.1–1 s in time and ∼100 km in space at the equator). Variations between precipitation L‐shell profiles at intermediate inter‐satellite separations, a few seconds to about 1 min, are likely associated with whistler‐mode wave power modulations by ultra‐low frequency waves, that is, with the wave source region (from a few to tens of seconds to a few minutes in time and ∼1,000 km in space at the equator). During these two types of variations, consecutive crossings are associated with precipitation L‐shell profiles very similar to each other. Therefore the spatial and temporal variations at those scales do not change the net electron loss from the outer radiation belt. Variations at the largest range of inter‐satellite separations, several minutes to more than 10 min, are likely associated with mesoscale equatorial plasma structures that are affected by convection (at minutes to tens of minutes temporal variations and ≈[103, 104] km spatial scales). The latter type of variations results in appreciable changes in the precipitation L‐shell profiles and can significantly modify the net electron losses during successive tracks. Thus, such mesoscale variations should be included in simulations of the radiation belt dynamics.

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On the role of ULF waves in the spatial and temporal periodicity of energetic electron precipitation

Shi

Zhang²,

Artemyev³

et al. 2022

Preprint

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Energetic electron precipitation to the Earth's atmosphere is a key process controlling radiation belt dynamics and magnetosphereionosphere coupling. One of the main drivers of precipitation is electron resonant scattering by whistler-mode waves. Lowaltitude observations of such precipitation often reveal quasi-periodicity in the ultra-low-frequency (ULF) range associated with whistler-mode waves, causally linked to ULF-modulated equatorial electron flux and its anisotropy. Conjunctions between ground-based instruments and equatorial spacecraft show that low-altitude precipitation concurrent with equatorial whistlermode waves also exhibits a spatial periodicity as a function of latitude over a large spatial region. Whether this spatial periodicity might also be due to magnetospheric ULF waves spatially modulating electron fluxes and whistler-mode chorus has not been previously addressed due to a lack of conjunctions between equatorial spacecraft, LEO spacecraft, and ground-based instruments. To examine this question, we combine ground-based and equatorial observations magnetically conjugate to observations of precipitation at the low-altitude, polar-orbiting CubeSats ELFIN-A and -B. As they sequentially cross the outer radiation belt with a temporal separation of minutes to tens of minutes, they can easily reveal the spatial quasi-periodicity of electron precipitation. Our combined datasets confirm that ULF waves may modulate whistler-mode wave generation within a large MLT and $L$-shell domain in the equatorial magnetosphere, and thus lead to significant aggregate energetic electron precipitation exhibiting both temporal and spatial periodicity. Our results suggest that the coupling between ULF and whistler-mode waves is important for outer radiation belt dynamics.

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Nonlinear Wave Growth Analysis of Chorus Emissions Modulated by ULF Waves

Cited by 18 publications

References 93 publications

On the Role of ULF Waves in the Spatial and Temporal Periodicity of Energetic Electron Precipitation

On the Role of ULF Waves in the Spatial and Temporal Periodicity of Energetic Electron Precipitation

Temporal Scales of Electron Precipitation Driven by Whistler‐Mode Waves

On the role of ULF waves in the spatial and temporal periodicity of energetic electron precipitation

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