Nonlinear pitch angle scattering of energetic electrons by coherent VLF waves in the magnetosphere

Journal Article · Sat Jul 01 04:00:00 EDT 1978 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA083iA07p03235· OSTI ID:7050183

Inan, U S; Bell, T F; Helliwell, R A

A computer simulation approach is used to study the nonlinear cyclotron resonant interaction of energetic electrons and coherent VLF waves, with special emphasis on the pitch angvle scattering of the particles. Complete equations of motion in an inhomogeneous magnetosphere are used, and the effects of various parameters are studied. Comparison is made with linear theory, and a quantitative and easy-to-use criterion to determine the applicabiliy of linear theory under any given conditions is presented. For example, in the case of equatorial scattering by a 5-kHz CW pulse near L=4 it is found that linear theory begins to break down when the wave amplitude exceeds 3 m..gamma... The full distribution of particles is simulated by test electrons appropriately distributed in energy and pitch angle. By computing the scattering of these test particles and integrating over energy and pitch angle, the precipitated flux is obtained. The method used is quite general and can be used for any particle distribution. It is shown that significant particle fluxes are precipitaed by waves of moderate intensity. For instance, energetic (1-2 keV) electron fluxes as high as approx.10/sup -1/ erg/cm/sup 2/ s can be precipitated by a CW wave of 10-m..gamma.. amplitude and 5-kHz frequency on the Lapprox. =4 field lines. Such fluxes appear to be measurable with presently available instruments. Since the energy density of the precipitated flux is 50 dB above that of the wave, the leverage involved in the wave-induced precipitation process is quite high. Our results indicate that coherent VLF waves can have a significant effect on the dynamics and lifetimes of energetic electrons trapped in the magnetosphere on magnetic shells illuminated by the waves.

• Research Organization: Radioscience Laboratory, Stanford University, Stanford, California 94305
• OSTI ID: 7050183
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 83:A7; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BREMSSTRAHLUNG
CHARGED-PARTICLE PRECIPITATION
CYCLOTRON RADIATION
DIFFERENTIAL EQUATIONS
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
ELECTRON PRECIPITATION
ELECTRONS
ELEMENTARY PARTICLES
EQUATIONS
EQUATIONS OF MOTION
FERMIONS
INCLINATION
LEPTONS
MAGNETOSPHERE
RADIATIONS
SCATTERING
TRAPPED ELECTRONS