Wave-particle interactions near. cap omega. /sub He+/ observed in GEOS 1 and 2 1. Propagation of ion cyclotron waves in He/sup +/ -rich plasma

Journal Article · Sat Aug 01 04:00:00 EDT 1981 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA086iA08p06755· OSTI ID:5880922

Young, D T; Perraut, S; Roux, A; De Villedary, C; Gendrin, R; Korth, A; Kremser, G; Jones, D

The GEOS 1 and 2 spacecraft contain a set of particle and wave detectors which allow for a very comprehensive study of wave-particle interactions occurring within the equatorial region of the magnetosphere. This paper is devoted to interactions involving protons in the energy range 20 keV to 300 keV and ULF waves with frequencies below the proton gyrofrequency. It is shown that mose of the ion cyclotron waves (ICW's) detected in this frequency range have spectra whose charcteristic frequencies are organized in the vicinity of the He/sup +/ gyrofrequency. Simultaneous measurements of the ion composition in the thermal energy range (E< or approx. =110 eV) show these waves to be clearly associated with the abundance of cold He/sup +/ as well as the anisotropy of ions above 20 keV. The general characteristics of these helium-associated ULF events are presented in case studies of four events. The interpretation of this phenomenon is given in the present paper in terms of the propagation of ICW's in a He/sup +/ -rich plasma. It is shown that the shape of the cold plasma dispersion curve (for both parallel and non-parallel propgation) can adequately explain the main characteristics of the observed waves (frequency spectrum, polarization) as well as the differences between observations made onboard GEOS 1 and GEOS 2. The generation conditions of ion cylotron waves in such a multi-component plasma, as well as their quasi-linear effects on both the cold He/sup +/ ions and the hot protons, are discussed in a companion paper.

• Research Organization: Physikalisches Institut, University of Bern, 3012 Bern, Switzerland
• OSTI ID: 5880922
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 86:A8; 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 PARTICLES
COLD PLASMA
CYCLOTRON RADIATION
DISPERSION RELATIONS
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
ENERGY SPECTRA
GEOMAGNETIC EQUATOR
GEOS SATELLITES
GYROFREQUENCY
HELIUM IONS
ION WAVES
IONIC COMPOSITION
IONS
MAGNETOSPHERE
PLASMA
PLASMA WAVES
POLARIZATION
RADIATIONS
RADIOWAVE RADIATION
SATELLITES
SPECTRA
WAVE PROPAGATION