HR: 0800h
AN: SM21A-0304    [Abstracts]
TI: The Effects of Plasma Density Irregularities on the Pitch Angle Scattering of Energetic Radiation Belt Electrons due to VLF Signals from Ground Based Transmitters.
AU: * Bell, T F
EM: bell@nova.stanford.edu
AF: Stanford University Star Lab, 357 Packard building, Stanford, CA 94305, United States
AU: Inan, U S
EM: inan@nova.stanford.edu
AF: Stanford University Star Lab, 357 Packard building, Stanford, CA 94305, United States
AU: Kulkarni, P
EM: pxk161@stanford.edu
AF: Stanford University Star Lab, 357 Packard building, Stanford, CA 94305, United States
AU: Parrot, M
EM: michel.parrot@lpce.fr
AF: LPCE, 3A Avenue de la recherche 45071 Cedex 2, Orleans, 45071, France
AB: On the basis of analytical models, it is commonly believed that VLF signals from powerful ground based transmitters determine the lifetimes of energetic radiation belt electrons (100 keV - 1.5 MeV) on L shells in the range 1.3 - 2.8 [e.g., Abel and Thorne, 1998]. The primary mechanism of interaction is believed to be gyro- resonance. To test this hypothesis, one needs to know the characteristics of the VLF signals in the radiation belts, as well as the characteristics of the energetic electron precipitation produced by these VLF signals. To these ends, Stanford University has recently carried out a series of experiments in which the 21.4 kHz signals from the US Navy transmitter in Hawaii (NPM) are keyed in a regular OFF/ON pattern designed to reveal any energetic electron precipitation that may be attributed to the transmitter signals. The subject of the present paper concerns the characteristics of the 21.4 kHz signals in the radiation belts. VLF plasma wave observations from the DEMETER spacecraft suggest that the plasma on the L shells illuminated by the NPM transmitter often contain small-scale magnetic-field-aligned plasma density irregularities. VLF waves propagating within these irregularities will generally excite lower-hybrid waves through linear mode coupling. At any given point along an L shell, the excited lower-hybrid waves will resonate with electrons of higher energy than those which resonate with the input wave. Thus the energetic electron precipitation signature due to an input VLF pulse will be different when magnetic-field-aligned plasma density irregularities are present. We compare the precipitation signatures obtained both with, and without, the irregularities and discuss how our results compare with steady state models such as that of [Abel and Thorne, 1998].
DE: 0654 Plasmas
DE: 0689 Wave propagation (2487, 3285, 4275, 4455, 6934)
DE: 2716 Energetic particles: precipitating
DE: 2774 Radiation belts
DE: 7807 Charged particle motion and acceleration
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting