Resonant scattering and resultant pitch angle evolution of relativistic electrons by plasmaspheric hiss

Ni, Binbin; Bortnik, J.; Thorne, R. M.; Ma, Qianli; Chen, Lunjin

doi:10.1002/2013ja019260

Cited by 201 publications

(271 citation statements)

References 44 publications

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“…The wave normal distribution of EMIC waves is also assumed to be Gaussian and given by [e.g., Glauert and Horne, 2005;Ni et al, 2013Ni et al, , 2014aNi et al, , 2014bKersten et al, 2014] …”

Section: Model Descriptionmentioning

confidence: 99%

“…In order to investigate the temporal evolution of outer zone relativistic electron pitch angle distribution due to EMIC wave scattering, we perform the 1-D pure pitch angle diffusion simulations [e.g., Meredith et al, 2006;Thorne et al, 2013;Ni et al, 2013Ni et al, , 2014aNi et al, , 2014b by numerically solving the equation where f is the phase space density (PSD), t is the time, and the electron bounce period is approximated as Lenchek et al, 1961]. The upper boundary condition for PSD in a eq space is set as ∂f ∂α eq α eq ¼ 90°À Á ¼ 0, and the corresponding lower boundary condition is set as ∂f ∂α eq α eq ¼ 0°À Á ¼ 0 for the strong diffusion and as f(α eq ≤ α LC ) = 0 (where α LC is the equatorial loss cone angle) for the weak diffusion.…”

Section: Pure Pitch Angle Diffusion Simulations and Electron Loss Timmentioning

confidence: 99%

“…The upper boundary condition for PSD in a eq space is set as ∂f ∂α eq α eq ¼ 90°À Á ¼ 0, and the corresponding lower boundary condition is set as ∂f ∂α eq α eq ¼ 0°À Á ¼ 0 for the strong diffusion and as f(α eq ≤ α LC ) = 0 (where α LC is the equatorial loss cone angle) for the weak diffusion. It is further assumed that the initial PSD follows a power law sinusoidal function of equatorial pitch angle, e.g., ∝ sin 1.5 α eq [e.g., Ni et al, 2013]. …”

Section: Pure Pitch Angle Diffusion Simulations and Electron Loss Timmentioning

confidence: 99%

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Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

et al. 2015

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To improve our understanding of the role of electromagnetic ion cyclotron (EMIC) waves in radiation belt electron dynamics, we perform a comprehensive analysis of EMIC wave‐induced resonant scattering of outer zone relativistic (>0.5 MeV) electrons and resultant electron loss time scales with respect to EMIC wave band, L shell, and wave normal angle model. The results demonstrate that while H+‐band EMIC waves dominate the scattering losses of ~1–4 MeV outer zone relativistic electrons, it is He+‐band and O+‐band waves that prevail over the pitch angle diffusion of ultrarelativistic electrons at higher energies. Given the wave amplitude, EMIC waves at higher L shells tend to resonantly interact with a larger population of outer zone relativistic electrons and drive their pitch angle scattering more efficiently. Obliquity of EMIC waves can reduce the efficiency of wave‐induced relativistic electron pitch angle scattering. Compared to the frequently adopted parallel or quasi‐parallel model, use of the latitudinally varying wave normal angle model produces the largest decrease in H+‐band EMIC wave scattering rates at pitch angles < ~40° for electrons > ~5 MeV. At a representative nominal amplitude of 1 nT, EMIC wave scattering produces the equilibrium state (i.e., the lowest normal mode under which electrons at the same energy but different pitch angles decay exponentially on the same time scale) of outer belt relativistic electrons within several to tens of minutes and the following exponential decay extending to higher pitch angles on time scales from <1 min to ~1 h. The electron loss cone can be either empty as a result of the weak diffusion or heavily/fully filled due to approaching the strong diffusion limit, while the trapped electron population at high pitch angles close to 90° remains intact because of no resonant scattering. In this manner, EMIC wave scattering has the potential to deepen the anisotropic distribution of outer zone relativistic electrons by reshaping their pitch angle profiles to “top‐hat.” Overall, H+‐band and He+‐band EMIC waves are most efficient in producing the pitch angle scattering loss of relativistic electrons at ~1–2 MeV. In contrast, the presence of O+‐band EMIC waves, while at a smaller occurrence rate, can dominate the scattering loss of 5–10 MeV electrons in the entire region of the outer zone, which should be considered in future modeling of the outer zone relativistic electron dynamics.

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“…The wave normal distribution of EMIC waves is also assumed to be Gaussian and given by [e.g., Glauert and Horne, 2005;Ni et al, 2013Ni et al, , 2014aNi et al, , 2014bKersten et al, 2014] …”

Section: Model Descriptionmentioning

confidence: 99%

Section: Pure Pitch Angle Diffusion Simulations and Electron Loss Timmentioning

confidence: 99%

Section: Pure Pitch Angle Diffusion Simulations and Electron Loss Timmentioning

confidence: 99%

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Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

et al. 2015

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“…Along the ray path (within 9 s), we compute the resonant energies of electrons for a range of equatorial pitch angle from 1 • ∼ 89 • with these highly oblique waves. We also investigate four resonance harmonics, i.e., N = −1, 0, 1, and 2, which should be the dominant resonances for interactions with whistler-mode waves (e.g., Shprits and Ni, 2009;Ni et al, 2013). Note that |N| > 2 can also occur for resonances with very high-energy electrons, while their contributions are relatively small compared to the resonance harmonics considered in this study.…”

Section: Resonance Condition For Interactions Of Artificially Triggermentioning

confidence: 95%

Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

Chang

Bortnik

et al. 2014

Ann. Geophys.

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Abstract. Modulated high-frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low-frequency (ELF)/very low-frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with highenergy electrons in the plasmasphere. By ray tracing the magnetospheric propagation of ELF/VLF emissions artificially generated at low-invariant latitudes, we evaluate the relativistic electron resonant energies along the ray paths and show that propagating artificial ELF/VLF waves can resonate with electrons from ∼ 100 keV to ∼ 10 MeV. We further implement test particle simulations to investigate the effects of resonant scattering of energetic electrons due to triggered monotonic/single-frequency ELF/VLF waves. The results indicate that within the period of a resonance timescale, changes in electron pitch angle and kinetic energy are stochastic, and the overall effect is cumulative, that is, the changes averaged over all test electrons increase monotonically with time. The localized rates of wave-induced pitch-angle scattering and momentum diffusion in the plasmasphere are analyzed in detail for artificially generated ELF/VLF whistlers with an observable in situ amplitude of ∼ 10 pT. While the local momentum diffusion of relativistic electrons is small, with a rate of < 10 −7 s −1 , the local pitchangle scattering can be intense near the loss cone with a rate of ∼ 10 −4 s −1 . Our investigation further supports the feasibility of artificial triggering of ELF/VLF whistler waves for removal of high-energy electrons at lower L shells within the plasmasphere. Moreover, our test particle simulation results show quantitatively good agreement with quasi-linear diffusion coefficients, confirming the applicability of both methods to evaluate the resonant diffusion effect of artificial generated ELF/VLF whistlers.

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“…Various processes can determine the radiation belt dynamics, including wave-driven acceleration or loss processes (Summers et al 1998(Summers et al , 2007aAlbert et al 2009;Gu et al 2012;Li et al 2007;Ni et al 2013Ni et al , 2014aSu et al 2009Su et al , 2010Su et al , 2011aSu et al , 2011bXiao et al 2006aXiao et al , 2010Xiao et al , 2011, and radial diffusion process associated with ultra low frequency (ULF) waves (Hudson et al 2000;Thorne 2010;Elkington et al 2003). In general, hiss or electromagnetic ion cyclotron (EMIC) waves can produce pitch angle scattering of relativistic (MeV) electrons, whereas chorus or Z-mode or fast Magnetosonic (MS) waves can yield efficient acceleration of relativistic (MeV) electrons ; Thorne et al 2013;Gao et al 2014;Xiao et al 2012Xiao et al , 2014aYan et al 2013;Yang et al 2014;Zhang et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Effect of chorus normal angle on dynamic evolution of radiation belt energetic electrons

Zhang

Yang

et al. 2014

Astrophys Space Sci

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Gyroresonance between chorus waves and radiation belt electrons is usually evaluated by using the Gaussian wave normal angle (X = tan θ ) distribution. In this study, we examine the influence of peak wave normal angle (X m = tan θ m ) on chorus-electron interaction in the heart of radiation belts L = 4.5. By varying X m = 0, 2, 4, 6, we calculate the bounce-averaged diffusion coefficients, and then simulate the phase space density (PSD) evolution of radiation belt energetic electrons induced by both dayside and nightside chorus waves. Numerical simulations show that diffusion coefficients move to the low pitch angle region and drop rapidly by a factor of ∼ 10 as X m increases by 2 each time, consequently leading to the smaller amplitude and narrower pitch angle region in electron PSD evolution. The current results demonstrate that chorus-electron interaction in the outer radiation belt is largely dependent on peak wave normal angles.

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Resonant scattering and resultant pitch angle evolution of relativistic electrons by plasmaspheric hiss

Cited by 201 publications

References 44 publications

Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

Effect of chorus normal angle on dynamic evolution of radiation belt energetic electrons

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