Pitch-angle diffusion of electrons through growing and propagating along a magnetic field electromagnetic wave in Earth's radiation belts

2015 ◽  
Vol 22 (6) ◽  
pp. 062903 ◽  
Author(s):  
C.-R. Choi ◽  
M.-H. Woo ◽  
K. Dokgo ◽  
E.-J. Choi ◽  
K.-W. Min ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Pitch Angle ◽  
Radiation Belts ◽  
Earth's Radiation Belts

scholarly journals Pitch angle scattering of an energetic magnetized particle by a circularly polarized electromagnetic wave

2021 ◽  
Author(s):  
Paul M. Bellan
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Kinetic Energy ◽  
Potential Energy ◽  
Pitch Angle ◽  
Energetic Electron ◽  
Circularly Polarized ◽  
Angle Scattering ◽  
Background Magnetic Field ◽  
Pseudo Potential

<p>The interaction between a circularly polarized electromagnetic wave and an energetic gyrating particle is described [1] using a relativistic pseudo-potential that is a function of the frequency mismatch,  a measure of the extent to which ω-k<sub>z</sub>v<sub>z</sub>=Ω/γ is not true. The description of this wave-particle interaction involves a sequence of relativistic transformations that ultimately demonstrate that the pseudo potential energy of a pseudo particle adds to a pseudo kinetic energy giving a total pseudo energy that is a constant of the motion. The pseudo kinetic energy is proportional to the square of the particle acceleration (compare to normal kinetic energy which is the square of a velocity) and the pseudo potential energy is a function of the mismatch and so effectively a function of the particle velocity parallel to the background magnetic field (compare to normal potential energy which is a function of position). Analysis of the pseudo-potential provides a means for interpreting particle motion in the wave in a manner analogous to the analysis of a normal particle bouncing in a conventional potential well.  The wave-particle  interaction is electromagnetic and so differs from and is more complicated than the well-known Landau damping of electrostatic waves.  The pseudo-potential profile depends on the initial mismatch, the normalized wave amplitude, and the initial angle between the wave magnetic field and the particle perpendicular velocity. For zero initial mismatch, the pseudo-potential consists of only one valley, but for finite mismatch, there can be two valleys separated by a hill. A large pitch angle scattering of the energetic electron can occur in the two-valley situation but fast scattering can also occur in a single valley. Examples relevant to magnetospheric whistler waves are discussed. Extension to the situation of a distribution of relativistic particles is presented in a companion talk [2].</p><p>[1] P. M. Bellan, Phys. Plasmas 20, Art. No. 042117 (2013)</p><p>[2] Y. D. Yoon and P. M. Bellan, JGR 125, Art. No. e2020JA027796 (2020)</p>

scholarly journals POLAR spacecraft observations of helium ion angular anisotropy in the Earth's radiation belts

1999 ◽  
Vol 17 (6) ◽  
pp. 723-733 ◽  
Author(s):  
W. N. Spjeldvik ◽  
T. A. Fritz ◽  
J. Chen ◽  
R. B. Sheldon
Keyword(s):  
Local Time ◽  
Pitch Angle ◽  
Radiation Belt ◽  
Radiation Belts ◽  
Magnetic Local Time ◽  
Angle Distribution ◽  
Pitch Angle Distribution ◽  
Helium Ion ◽  
Earth’S Radiation Belt ◽  
Earth's Radiation Belts

Abstract. New observations of energetic helium ion fluxes in the Earth's radiation belts have been obtained with the CAMMICE/HIT instrument on the ISTP/GGS POLAR spacecraft during the extended geomagnetically low activity period April through October 1996. POLAR executes a high inclination trajectory that crosses over both polar cap regions and passes over the geomagnetic equator in the heart of the radiation belts. The latter attribute makes possible direct observations of nearly the full equatorial helium ion pitch angle distributions in the heart of the Earth's radiation belt region. Additionally, the spacecraft often re-encounters the same geomagnetic flux tube at a substantially off-equatorial location within a few tens of minutes prior to or after the equatorial crossing. This makes both the equatorial pitch angle distribution and an expanded view of the local off-equatorial pitch angle distribution observable. The orbit of POLAR also permitted observations to be made in conjugate magnetic local time sectors over the course of the same day, and this afforded direct comparison of observations on diametrically opposite locations in the Earth's radiation belt region at closely spaced times. Results from four helium ion data channels covering ion kinetic energies from 520 to 8200 KeV show that the distributions display trapped particle characteristics with angular flux peaks for equatorially mirroring particles as one might reasonably expect. However, the helium ion pitch angle distributions generally flattened out for equatorial pitch angles below about 45°. Significant and systematic helium ion anisotropy difference at conjugate magnetic local time were also observed, and we report quiet time azimuthal variations of the anisotropy index.Key words. Magnetospheric physics (energetic particles · trapped; magnetospheric configuration and dynamics; plasmasphere)

Effect of finite correlation time on the wave-particle interactions of nonlinear electrostatic structures with electrons in the Earth's radiation belts.

2020 ◽  
Author(s):  
Adnane Osmane
Keyword(s):  
Phase Space ◽  
Pitch Angle ◽  
Radiation Belts ◽  
Particle Interactions ◽  
Chorus Waves ◽  
Angle Scattering ◽  
Open Question ◽  
Finite Correlation ◽  
Earth's Radiation Belts

<p><em>In situ</em> measurements of electron scale fluctuations by the Van Allen Probes and MMS have demonstrated the ubiquitous occurrence of phase-space holes and various kinetic nonlinear structures in the Earth's magnetosphere. However it remains an open question whether phase-space holes have to be incorporated into global magnetospheric models describing the energisation and acceleration of electrons. In this communication we will review current wave-particle models of electron phase-space holes interacting with energetic electrons (e.g. >1 keV in the Earth's radiation belts)  and present new theoretical results showing that finite correlation times of phase-space holes results in enhanced pitch-angle scattering. The pitch-angle scattering by phase-space holes is shown to be on par with that produced by chorus waves, and in some instances outgrows the chorus contribution. </p><p> </p>

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