scholarly journals Evidence of stronger pitch angle scattering loss caused by oblique whistler-mode waves as compared with quasi-parallel waves

2014 ◽  
Vol 41 (17) ◽  
pp. 6063-6070 ◽  
Author(s):  
W. Li ◽  
D. Mourenas ◽  
A. V. Artemyev ◽  
O. V. Agapitov ◽  
J. Bortnik ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Whistler Mode ◽  
Scattering Loss ◽  
Angle Scattering ◽  
Whistler Mode Waves

scholarly journals Pitch Angle Scattering of Upgoing Electron Beams in Jupiter's Polar Regions by Whistler Mode Waves

2018 ◽  
Vol 45 (3) ◽  
pp. 1246-1252 ◽  
Author(s):  
S. S. Elliott ◽  
D. A. Gurnett ◽  
W. S. Kurth ◽  
G. Clark ◽  
B. H. Mauk ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Electron Beams ◽  
Polar Regions ◽  
Whistler Mode ◽  
Angle Scattering ◽  
Whistler Mode Waves

Electron Pitch Angle Distributions in the Compressional Pc5 Waves

2021 ◽  
Author(s):  
Xiao Ma ◽  
Anmin Tian ◽  
Quanqi Shi ◽  
Shichen Bai ◽  
Ji Liu ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Interaction Effects ◽  
Plasma Pressure ◽  
Whistler Waves ◽  
Whistler Mode ◽  
Compressional Waves ◽  
The Earth ◽  
Pressure Anisotropy ◽  
Electron Distributions ◽  
Whistler Mode Waves

<p>In the two flanks of the Earth’s magnetosphere, the compressional Pc5 waves are often observed. Previous study suggests that these waves are usually excited by plasma pressure anisotropy such as drift mirror instability. Interestingly, whistler mode waves are often observed in the magnetic trough regions of the compressional Pc5 waves. In this study, we use 10 years (2007-2016) THEMIS A data to study the electron distributions in the compressional Pc5 waves associated with the whistler mode waves. We find three typical electron pitch angle distributions (PADs) in these compressional waves: cigar-shape, donut-shape and pancake-shape. They predominantly occur at tens to hundreds eV, several keV and >10 keV, respectively. The interaction effects between the electrons and whistler waves inside the magnetic troughs are stressed in understanding the formation of these PADs.</p>

scholarly journals The generation of Ganymede's diffuse aurora through pitch angle scattering

2017 ◽  
Vol 35 (2) ◽  
pp. 239-252
Author(s):  
Arvind K. Tripathi ◽  
Rajendra P. Singhal ◽  
Onkar N. Singh II
Keyword(s):  
Electron Temperature ◽  
Pitch Angle ◽  
Atomic Oxygen ◽  
Particle Interaction ◽  
Distribution Functions ◽  
Dissociative Excitation ◽  
Kappa Distribution ◽  
Loss Cone ◽  
Whistler Mode ◽  
Whistler Mode Waves

Abstract. Diffuse auroral intensities of neutral atomic oxygen OI λ1356 Å emission on Ganymede due to whistler mode waves are estimated. Pitch angle diffusion of magnetospheric electrons into the loss cone due to resonant wave–particle interaction of whistler mode waves is considered, and the resulting electron precipitation flux is calculated. The analytical yield spectrum approach is used for determining the energy deposition of electrons precipitating into the atmosphere of Ganymede. It is found that the intensities (4–30 R) calculated from the precipitation of magnetospheric electrons observed near Ganymede are inadequate to account for the observational intensities (≤ 100 R). This is in agreement with the conclusions reached in previous works. Some acceleration mechanism is required to energize the magnetospheric electrons. In the present work we consider the heating and acceleration of magnetospheric electrons by electrostatic waves. Two particle distribution functions (Maxwellian and kappa distribution) are used to simulate heating and acceleration of electrons. Precipitation of a Maxwellian distribution of electrons can produce about 70 R intensities of OI λ1356 Å emission for electron temperature of 150 eV. A kappa distribution can also yield a diffuse auroral intensity of similar magnitude for a characteristic energy of about 100 eV. The maximum contribution to the estimated intensity results from the dissociative excitation of O2. Contributions from the direct excitation of atomic oxygen and cascading in atomic oxygen are estimated to be only about 1 and 2 % of the total calculated intensity, respectively. The findings of this work are relevant for the present JUNO and future JUICE missions to Jupiter. These missions will provide new data on electron densities, electron temperature and whistler mode wave amplitudes in the magnetosphere of Jupiter near Ganymede.

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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