All Physics Faculty Publications
Document Type
Article
Journal/Book Title/Conference
Journal of Geophysical Research
Volume
88
Issue
A2
Publisher
American Geophysical Union
Publication Date
1983
First Page
889
Last Page
898
Abstract
Ion cyclotron waves (ICWs) at frequencies just above f He+ , the helium gyrofrequency, are often observed by the ESA satellites GEOS 1 and GEOS 2. Young et al. (1981) have shown the close connection between these ICWs and the presence of thermal He+ ions in the outer magnetosphere. The purpose of this paper is to provide experimental evidence for the acceleration of thermal electrons by the large amplitude ICWs. The wave power in the ultra low frequency (ULF) range near f He+ is compared with the distribution function of low energy electrons, measured by instruments aboard the GEOS satellites. It shows that, near the geomagnetic equator, electrons are accelerated along field lines at times when the ICW energy is large and the cold plasma density is below a threshold value. It is suggested that these accelerated electrons can account for the ELF emissions, modulated at the ICWs frequency, observed by Cornilleau-Wehrlin (1981). Other ULF events having frequencies close to the proton gyrofrequency f H+ are also observed and result in a very efficient acceleration of thermal electrons along field lines. The evidence in this case is that medium energy protons having large temperature anisotropies (T ⊥ ≫ T ∥) in the 100- to 500-eV range are responsible for the ICW wave generation.
Recommended Citation
Norris, A. J., J. F. E. Johnson, J. J. Sojka, G. L. Wrenn, N. Cornilleau-Wehrlin, S. Perraut, and A. Roux (1983), Experimental Evidence for the Acceleration of Thermal Electrons by Ion Cyclotron Waves in the Magnetosphere, J. Geophys. Res., 88(A2), 889–898, doi:10.1029/JA088iA02p00889.
Comments
Originally published by theAmerican Geophysical Union. This article appeared in the Journal of Geophysical Research: Space Science.