Quasi-linear diffusion coefficients for highly oblique whistler mode waves

2017 ◽  
Vol 122 (5) ◽  
pp. 5339-5354 ◽  
Author(s):  
J. M. Albert
Keyword(s):  
Diffusion Coefficients ◽  
Linear Diffusion ◽  
Whistler Mode ◽  
Whistler Mode Waves

scholarly journals Long-term evolution of electron distribution function due to nonlinear resonant interaction with whistler mode waves

2018 ◽  
Vol 84 (2) ◽  
Author(s):  
Anton V. Artemyev ◽  
Anatoly I. Neishtadt ◽  
Alexei A. Vasiliev ◽  
Didier Mourenas
Keyword(s):  
Kinetic Equation ◽  
Electron Distribution ◽  
Resonant Interaction ◽  
Long Term Evolution ◽  
Radiation Belts ◽  
Linear Diffusion ◽  
Whistler Mode ◽  
Term Evolution ◽  
Whistler Mode Waves

Accurately modelling and forecasting of the dynamics of the Earth’s radiation belts with the available computer resources represents an important challenge that still requires significant advances in the theoretical plasma physics field of wave–particle resonant interaction. Energetic electron acceleration or scattering into the Earth’s atmosphere are essentially controlled by their resonances with electromagnetic whistler mode waves. The quasi-linear diffusion equation describes well this resonant interaction for low intensity waves. During the last decade, however, spacecraft observations in the radiation belts have revealed a large number of whistler mode waves with sufficiently high intensity to interact with electrons in the nonlinear regime. A kinetic equation including such nonlinear wave–particle interactions and describing the long-term evolution of the electron distribution is the focus of the present paper. Using the Hamiltonian theory of resonant phenomena, we describe individual electron resonance with an intense coherent whistler mode wave. The derived characteristics of such a resonance are incorporated into a generalized kinetic equation which includes non-local transport in energy space. This transport is produced by resonant electron trapping and nonlinear acceleration. We describe the methods allowing the construction of nonlinear resonant terms in the kinetic equation and discuss possible applications of this equation.

Electron pitch-angle diffusion driven by oblique whistler-mode turbulence

1971 ◽  
Vol 6 (3) ◽  
pp. 589-606 ◽  
Author(s):  
L. R. Lyons ◽  
R. M. Thorne ◽  
C. F. Kennel
Keyword(s):  
Wave Energy ◽  
Diffusion Coefficients ◽  
Pitch Angle ◽  
High Energy ◽  
Harmonic Number ◽  
General Description ◽  
Linear Diffusion ◽  
Whistler Mode ◽  
Angle Scattering ◽  
Cyclotron Harmonic

A general description of cyclotron harmonic resonant pitch-angle scattering is presented. Quasi-linear diffusion coefficients are prescribed in terms of the wave normal distribution of plasma wave energy. Numerical computations are performed for the specific case of relativistic electrons interacting with a band of low frequency whistler-mode turbulence. A parametric treatment of the wave energy distribution permits normalized diffusion coefficients to be presented graphically solely as a function of the electron pitch-angle.The diffusion coefficients generally decrease with increasing cyclotron harmonic number. Higher harmonic diffusion is insignificant at very small electron pitch-angles, but becomes increasingly important as the pitch-angle increases. One thus expected the rate of pitch-angle scattering to decrease with increasing electron energy, since the resonant value of the latter varies proportionately with harmonic number. This indicates that, in mirror-type magnet field geometrics, such as the Earth's radiation belts, the diffusion losses of high energy electrons are likely to be appreciably slower than those at low energy. Integration of the diffusion rates along a complete bounce orbit will be required to clarify this point, however, since the high-energy particles will be subject to more rapid first harmonic diffusion near their mirror points.

scholarly journals Study of whistler mode instability in Saturn's magnetosphere

2006 ◽  
Vol 24 (6) ◽  
pp. 1705-1712 ◽  
Author(s):  
R. P. Singhal ◽  
A. K. Tripathi
Keyword(s):  
Diffusion Coefficients ◽  
Pitch Angle ◽  
Temperature Anisotropy ◽  
Mode Instability ◽  
Whistler Mode ◽  
Energy Diffusion ◽  
Whistler Mode Waves ◽  
Magnetosphere Of Saturn ◽  
Temporal Growth Rate ◽  
Good Agreement

Abstract. A dispersion relation for parallel propagating whistler mode waves has been applied to the magnetosphere of Saturn and comparisons have been made with the observations made by Voyager and Cassini. The effect of hot (suprathermal) electron-density, temperature, temperature anisotropy, and the spectral index parameter, κ, on the temporal growth rate of the whistler mode emission is studied. A good agreement is found with observations. Electron pitch angle and energy diffusion coefficients have been obtained using the calculated temporal growth rates.

Statistical Study of Pitch Angle Diffusion during Substorm Injections

2020 ◽  
Author(s):  
Reihaneh Ghaffari ◽  
Christopher Cully
Keyword(s):  
Pitch Angle ◽  
Energetic Electron ◽  
Loss Cone ◽  
Linear Diffusion ◽  
Whistler Mode ◽  
Wave Measurements ◽  
Whistler Mode Waves ◽  
Substorm Injection ◽  
Injection Region

<p>Energetic Electron Precipitation (EEP) associated with substorm injections typically occurs when magnetospheric waves, particularly whistler-mode waves, resonantly interact with electrons to affect their equatorial pitch angle. This can be considered as a diffusion process that scatters particles into the loss cone. In this study, we investigate whistler-mode wave generation in conjunction with electron injections using in-situ wave measurements by the Themis mission. We calculate the pitch angle diffusion coefficient exerted by the observed wave activity using the quasi-linear diffusion approximation and estimate scattering efficiency in the substorm injection region to constrain where and how much scattering happens typically during these events.</p>

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