Electron distribution functions associated with electrostatic emissions in the dayside magnetosphere

Journal Article · Mon Oct 01 04:00:00 EDT 1979 · Geophys. Res. Lett.; (United States)

DOI:https://doi.org/10.1029/GL006i010p00781· OSTI ID:5910204

Sentman, D D; Frank, L A; Gurnett, D A; Kurth, W S; Kennel, C F

Electron distribution functions constructed from ISEE-1 dayside observations of low energy magnetospheric electrons at low latitudes are presented. We choose examples corresponding to three distinct types of odd half harmonic electrostatic emissions observed by the plasma wave experiment on ISEE-1, and occurring between the electron cyclotron frequency f/sub ce/ and the upper hybrid frequency f/sub UH/. These are (a) intense (3/2) f/sub ce/ emissions; (b) weak (n+1/2) f/sub ce/ noise; and (c) intense f/sub UH/ waves at (9/2) f/sub ce/. No loss cone-like features are discernable in any of the distribution functions at the level of the instrument angular resolution. However, a weak ringlike feature, consisting of a small localized region in velocity space near 4 x 10/sup 9/ cm s/sup -1/ and ..cap alpha..=90/sup 0/ where partialf/partial..nu../sub perpendicular/>0, is found in the distribution function corresponding to the occurrence of the intense f/sub UH/ noise. This ringlike feature may provide a source of free energy to drive the f/sub UH/ instability. The apparent absence of detectable loss cones in the cases of the intense (3/2) f/sub ce/ and f/sub UH/ emissions is consistent with the expectation that these plasmas are roughly at the level of strong pitch angle diffusion computed from the observed wave intensities at these times. Although each of the distribution functions displays a temperature anisotropy T/sub perpendicular/>T/sub parallel/, the anisotropies are too small to excite any of the odd half harmonic emissions.

• Research Organization: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90024
• OSTI ID: 5910204
• Journal Information: Geophys. Res. Lett.; (United States), Journal Name: Geophys. Res. Lett.; (United States) Vol. 6:10; ISSN GPRLA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DIFFUSION
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
ELECTRONS
ELEMENTARY PARTICLES
ENERGY
FERMIONS
FREE ENERGY
GYROFREQUENCY
INSTABILITY
LEPTONS
MAGNETOSPHERE
PHYSICAL PROPERTIES
PLASMA INSTABILITY
PLASMA WAVES
THERMODYNAMIC PROPERTIES