Ion Dynamics During the Parametric Instabilities of a Left-Hand Polarized Alfvén Wave in a Proton-Electron-Alpha Plasma

Gao, Xinliang; Lu, Quanming; Li, Xing; Hao, Yufei; Tao, X.; Wang, Shui

doi:10.1088/0004-637x/780/1/56

Cited by 13 publications

(11 citation statements)

References 56 publications

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“…The bicoherence analysis is a widely used method to identify the underlying wave‐wave interactions in a plasma system. The analysis can measure the phase relation among three magnetosonic waves (Gao et al, , ; Milligen et al, ). Here we choose the parallel component of fluctuating magnetic fields δB y at two wavenumbers k By and k w and one perpendicular component of electric fields δE x at the wavenumber k w = k Ex + k By to calculate the bicoherence index, which is defined as

bc ((),, k_{italicEx}, k_{italicBy}) = \frac{{(||, 〈δ E_{x} (k_{Ex}) δ B_{y} (k_{By}) δ B_{y}^{*} (k_{w})〉)}^{2}}{(〈〉, {(||, δ E_{x} ((), k_{italicEx}) δ B_{y} ((), k_{italicBy}))}^{2}) (〈〉, {(||, {δB}_{y}^{*} ((), k_{w}))}^{2})},

where the bracket 〈〉 denotes an average over the time interval of 10–20

Ω_{h}^{- 1}

.…”

Section: Simulation Resultsmentioning

confidence: 99%

Generation of Lower Harmonic Magnetosonic Waves Through Nonlinear Wave‐Wave Interactions

Gao

Sun

et al. 2018

Geophysical Research Letters

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Although magnetosonic waves in the Earth's magnetosphere have been well understood by the linear theory, low harmonic magnetosonic waves, which often lack of free energy, can be unusually present. By employing a 1‐D particle‐in‐cell simulation model, we have investigated the generation of those unusual lower harmonic magnetosonic waves in a plasma containing a proton ring distribution. In our simulation, the higher harmonic magnetosonic waves (from~9Ωh to ~12Ωh) are firstly excited due to the unstable proton ring, which can be well explained by the linear theory. Several lower harmonic magnetosonic waves (below 5Ωh), which well separates away from the higher harmonics, soon appear in the system. Those lower harmonics, which do not have any positive linear growth rates, can be generated by a nonlinear mechanism. The bicoherence analysis demonstrates that there is a strong phase coupling among the unusual lower harmonic magnetosonic waves and the magnetosonic waves generated due to the proton ring, supporting the idea that the lower harmonic waves could be driven by the wave‐wave couplings of the generated magnetosonic waves. This wave‐wave coupling generation mechanism is further confirmed by another two simulations, where two or three pump magnetosonic waves are initially injected. The lower‐frequency waves, that is, the fundamental wave and its second harmonic, are also successfully reproduced due to the nonlinear coupling of pump magnetosonic waves. Our simulations not only propose a potential generation mechanism of unusual lower harmonic magnetosonic waves in the Earth's magnetosphere, but also give some new insights on the evolution of magnetosonic spectra.

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bc ((),, k_{italicEx}, k_{italicBy}) = \frac{{(||, 〈δ E_{x} (k_{Ex}) δ B_{y} (k_{By}) δ B_{y}^{*} (k_{w})〉)}^{2}}{(〈〉, {(||, δ E_{x} ((), k_{italicEx}) δ B_{y} ((), k_{italicBy}))}^{2}) (〈〉, {(||, {δB}_{y}^{*} ((), k_{w}))}^{2})},

where the bracket 〈〉 denotes an average over the time interval of 10–20

Ω_{h}^{- 1}

.…”

Section: Simulation Resultsmentioning

confidence: 99%

Generation of Lower Harmonic Magnetosonic Waves Through Nonlinear Wave‐Wave Interactions

Gao

Sun

et al. 2018

Geophysical Research Letters

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“…Figure shows the bicoherence index between the electromagnetic ( δE y ) and electrostatic ( δE x ) components of whistler mode waves for Ω e t = 300–350, when upper band harmonic waves reach the saturation. The bicoherence index is a widely used method to quantify the resonant condition among three waves (Gao, Lu, et al, ; Gao et al, ; Gao, Ke, et al, ; Gao, Lu, & Wang, ; Nariyuki & Hada, ; Nariyuki et al, ; van Milligen et al, ), which is given by

{|(〈〉, δ E_{x} ((), k_{italicEx}) δ E_{y} ((), k_{italicEy}) δ E_{y}^{*} ((), k_{HW}))|}^{2} / (〈〉, {(||, δ E_{x} ((), k_{italicEx}) δ E_{y} ((), k_{italicEy}))}^{2}) (〈〉, {(||, δ E_{y}^{*} ((), k_{HW}))}^{2})

(where k HW = k Ex + k Ey , k Ey and k Ex are wave numbers of the electromagnetic ( δE y ) and electrostatic ( δE x ) components of lower band whistler mode waves, respectively, and the bracket ⟨…⟩ denotes an average over a 50

Ω_{e}^{- 1}

time interval) in this study. The black dashed line in this panel marks the peak wave number of upper band waves, that is, k Ex + k Ey = 1.30( V Ae /Ω e ) −1 , where is also the high‐bc region.…”

Section: Simulation Resultsmentioning

confidence: 99%

Lower Band Cascade of Whistler Waves Excited by Anisotropic Hot Electrons: One‐Dimensional PIC Simulations

Chen

Gao

et al. 2017

JGR Space Physics

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Based on Time History of Events and Macroscale Interactions during Substorms waveform data, Gao, Lu, et al. (2016) have reported two special multiband chorus events, where upper band waves are located at harmonics of lower band waves. And they proposed a new generation mechanism to explain this multiband chorus wave, named as lower band cascade. With a 1‐D particle‐in‐cell (PIC) simulation model, we have investigated the lower band cascade of whistler waves excited by anisotropic hot electrons. During each simulation, lower band whistler mode waves are firstly excited by the anisotropy of hot electrons. Later, upper band harmonic waves are generated through the nonlinear coupling between the electromagnetic and electrostatic components of lower band waves, which supports the scenario of lower band cascade. Moreover, the peak wave number (or frequency) of lower band waves will continuously drift to smaller values due to the decline of the anisotropy of hot electrons. While the peak wave number of upper band harmonic waves will be kept nearly unchanged, but their amplitude continues to decrease after their saturation. We further find that the magnetic amplitude of upper band harmonic waves tends to increase with the increase of the wave normal angle of lower band waves or the anisotropy of hot electrons. Besides, the amplitude ratio between upper band and lower band waves is positively correlated with the wave normal angle of lower band waves but is anticorrelated with the anisotropy of hot electrons. Our study has provided a more comprehensive understanding of the lower band cascade of whistler waves.

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“…Such an instability is certainly more likely to contribute to wave generation at very low frequencies where the amplitude of the anti-sunward propagating Alfvén waves is strong. The contribution of such instabilities to the wave generation at ion kinetic scales studied in this work is more difficult but has been discussed in numerical simulations (Matteini et al 2010;Gao et al 2014). However, the parametric instability is not expected to account for the observed increase of the power ratio at 1 < kv A /Ω p < 1 since (anti-sunward) sound waves are subject to Landau damping while the daughter Alfvén waves are subject to less damping in a warm plasma such as the solar wind at 1AU.…”

Section: Discussionmentioning

confidence: 99%

A STATISTICAL STUDY OF THE SOLAR WIND TURBULENCE AT ION KINETIC SCALES USING THEK-FILTERING TECHNIQUE AND CLUSTER DATA

Roberts

Jeska

2015

ApJ

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Plasma turbulence at ion kinetic scales in the solar wind is investigated using the multi-point magnetometer data from the Cluster spacecraft. By applying the k-filtering method, we are able to estimate the full three-dimensional power spectral density P (ω sc , k) at a certain spacecraft frequency ω sc in wavevector (k) space. By using the wavevector at the maximum power in P (ω sc , k) at each sampling frequency ω sc and the Doppler shifted frequency ω pla in the solar wind frame, the dispersion plot ω pla = ω pla (k) is found. Previous studies have been limited to very few intervals and have been hampered by large errors, which motivates a statistical study of 52 intervals of solar wind. We find that the turbulence is predominantly highly oblique to the magnetic field k ⊥ k , and propagates slowly in the plasma frame with most points having frequencies smaller than the proton gyrofrequency ω pla < Ω p . Weak agreement is found that turbulence at the ion kinetic scales consists of kinetic Alfvén waves and coherent structures advected with plasma bulk velocity plus some minor more compressible components. The results suggest that anti-sunward and sunward propagating magnetic fluctuations are of similar nature in both the fast and slow solar wind at ion kinetic scales. The fast wind has significantly more anti-sunward flux than sunward flux and the slow wind appears to be more balanced.

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Ion Dynamics During the Parametric Instabilities of a Left-Hand Polarized Alfvén Wave in a Proton-Electron-Alpha Plasma

Cited by 13 publications

References 56 publications

Generation of Lower Harmonic Magnetosonic Waves Through Nonlinear Wave‐Wave Interactions

Generation of Lower Harmonic Magnetosonic Waves Through Nonlinear Wave‐Wave Interactions

Lower Band Cascade of Whistler Waves Excited by Anisotropic Hot Electrons: One‐Dimensional PIC Simulations

A STATISTICAL STUDY OF THE SOLAR WIND TURBULENCE AT ION KINETIC SCALES USING THEK-FILTERING TECHNIQUE AND CLUSTER DATA

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