Immediate Impact of Solar Wind Dynamic Pressure Pulses on Whistler‐Mode Chorus Waves in the Inner Magnetosphere

Jin, Yuyue; Liu, Nigang; Su, Zhenpeng; Zheng, Huinan; Wang, Yuming; Wang, Shui

doi:10.1029/2022gl097941

Cited by 8 publications

(13 citation statements)

References 82 publications

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“…Drift-shell splitting and other dynamic effects such as solar wind compression pulses can cause further wave excitation and scattering of particles into the loss cone (Jin et al. 2022 ; Ukhorskiy et al. 2014 ).…”

Section: Introductionmentioning

confidence: 99%

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

et al. 2023

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We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data collected by the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at >0.5 MeV which are abrupt (bursty) (lasting ∼17 s, or $\Delta L\sim 0.56$ Δ L ∼ 0.56 ) with significant substructure (occasionally down to sub-second timescale). We attribute the bursty nature of the precipitation to the spatial extent and structuredness of the wave field at the equator. Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Case studies employing conjugate ground-based or equatorial observations of the EMIC waves reveal that the energy of moderate and strong precipitation at ELFIN approximately agrees with theoretical expectations for cyclotron resonant interactions in a cold plasma. Using multiple years of ELFIN data uniformly distributed in local time, we assemble a statistical database of ∼50 events of strong EMIC wave-driven precipitation. Most reside at $L\sim 5-7$ L ∼ 5 − 7 at dusk, while a smaller subset exists at $L\sim 8-12$ L ∼ 8 − 12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an $L$ L -shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio’s spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of $\sim 1.45$ ∼ 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. It should be noted though that this diffusive treatment likely includes effects from nonlinear resonant interactions (especially at high energies) and nonresonant effects from sharp wave packet edges (at low energies). Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven >1 MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to ∼ 200-300 keV by much less intense higher frequency EMIC waves at dusk (where such waves are most frequent). At ∼100 keV, whistler-mode chorus may be implicated in concurrent precipitation. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.

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Section: Introductionmentioning

confidence: 99%

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

et al. 2023

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“…The peak linear convective growth rate of chorus waves in the Martian mini‐magnetospheres is approximately 10 −5 m −1 , two orders of magnitude higher than that in the Earth's inner magnetosphere (Jin et al., 2022; Omura, 2021; Su et al., 2018). When the waves grow linearly to a sufficiently high level, the nonlinear processes take place.…”

Section: Conclusion and Discussionmentioning

confidence: 96%

Inferring Whistler‐Mode Chorus Wave Source Regions in the Martian Mini‐Magnetospheres

Cheng,

Su,

et al. 2024

Geophysical Research Letters

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Martian mini‐magnetospheres contain whistler‐mode chorus waves potentially contributing to atmospheric escape, analogous to the Earth's inner magnetosphere. At Earth, the chorus waves have been found to originate from the near‐equatorial region spanning approximately 2% of the entire magnetic field line length. However, because of the lack of wave Poynting flux measurements, the Martian chorus source region remains unclear. By comparing the frequency dependence between observed wave power and modeled linear growth rates, we present the first attempt to explore the chorus wave source distribution along the Martian mini‐magnetospheric field lines. Our data‐to‐model comparisons support that these waves are not generated by a single source tightly confined near the magnetic strength minimal location but by intermittent or continuous sources spanning up to 40% of the entire field line length. These results imply that the Martian mini‐magnetospheres could have more active energy transfer processes mediated by whistler‐mode chorus waves than the expectation.

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“…The configuration of dayside magnetic field can be influenced by the solar wind dynamic pressure, which may further affect the electron anisotropy and geomagnetic field inhomogeneity. In some conditions, the electron betatron acceleration caused by the intensified geomagnetic field can lead to a higher anisotropy, thus providing more free energies to whistler‐mode waves (Fu et al., 2012; Jin et al., 2022). However, in another circumstances, the electronic anisotropy does not change significantly, while the variation of magnetic field inhomogeneity modulates the generation and disappearance of chorus waves (Liu et al., 2017; Zhou et al., 2015).…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Direct Observation of Rising‐Tone Chorus Triggered by Enhanced Solar Wind Pressure

Zhou,

Gao,

Chen

et al. 2023

JGR Space Physics

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Chorus waves play a significant role in both electron precipitation and acceleration in Earth's radiation belts. Their generation includes the initial linear process and subsequent nonlinear process. After the amplitude of whistler‐mode waves reaches a sufficient value in the linear phase, the nonlinear process takes effect and results in the frequency chirping of chorus waves. Here we present the first report on the generation and intensification of rising‐tone chorus driven by two sudden increases of solar wind dynamic pressure observed by Van Allen Probes on 20 December 2015. First, whistler‐mode waves are excited by the anisotropic thermal electrons (∼10s keV), which is quite consistent with the linear theoretical expectation. Then, rising‐tone chorus waves are nonlinearly generated from the existing whistler‐mode waves, triggered by the first increase of solar wind dynamic pressure. Subsequently, the second increase of solar wind pressure further intensifies the rising‐tone chorus. Based on the nonlinear theoretical model and Ts04 magnetic field model, we demonstrate that the decreasing inhomogeneity of the background magnetic field due to the increasing solar wind dynamic pressure is the major cause to trigger rising tones, which essentially reduces the wave amplitude threshold of the nonlinear process. Our study emphasizes the significance of solar wind dynamic pressure in the Earth's radiation belts from a micro perspective.

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Immediate Impact of Solar Wind Dynamic Pressure Pulses on Whistler‐Mode Chorus Waves in the Inner Magnetosphere

Cited by 8 publications

References 82 publications

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

Inferring Whistler‐Mode Chorus Wave Source Regions in the Martian Mini‐Magnetospheres

Direct Observation of Rising‐Tone Chorus Triggered by Enhanced Solar Wind Pressure

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