Journal article
Electron distribution functions associated with electrostatic emissions in the dayside magnetosphere
Geophysical research letters, Vol.6(10), pp.781-784
10/1979
DOI: 10.1029/GL006i010p00781
Abstract
Electron distribution functions constructed from ISEE-1 dayside observations of low energy magnetospheric electrons at low latitudes are presented. The authors 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(c) sub(e) and the upper hybrid frequency f sub(U) sub(H) . These are intense (3 /2)f sub(c) sub(e) emissions; weak (n+1/2)f sub(c) sub(e) noise; and intense f sub(U) sub(H) waves at (9/2)f sub(c) sub(e) . 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 super(9) cm sec super(-) super(1) and alpha =90 deg where delta f/ delta v sub() perpendicular > 0, is found in the distribution function corresponding to the occurrence of the intense f sub(U) sub(H) noise. This ringlike feature may provide a source of free energy to drive the f sub(U) sub(H) instability. The apparent absence of detectable loss cones in the cases of the intense (3/2)f sub(c) sub(e) and f sub(U) sub(H) emissions is consistent with the expectation that these plasmas are approximately 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 || >> , the anisotropies are too small to excite any of the odd half harmonic emissions.
Details
- Title: Subtitle
- Electron distribution functions associated with electrostatic emissions in the dayside magnetosphere
- Creators
- D D SentmanL. A. Frank - University of IowaD A Gurnett - University of Iowa, Physics and AstronomyW S Kurth - Physics and AstronomyC. F. Kennel - Chancellor University
- Resource Type
- Journal article
- Publication Details
- Geophysical research letters, Vol.6(10), pp.781-784
- DOI
- 10.1029/GL006i010p00781
- ISSN
- 0094-8276
- eISSN
- 1944-8007
- Language
- English
- Date published
- 10/1979
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984455282402771
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