Low-energy ion spectral peaks detected by CRRES in the plasma sheet
- Hanscom Air Force Base, MA (United States)
The authors have examined energy-versus time color spectrograms compiled by the low-energy plasma analyzer (LEPA) during 140 orbits of the Combined Release Radiation Effects Satellite (CRRES). Over the period of interest, the apogee of CRRES` orbit precessed from near dawn to near midnight. During more than half of the orbits LEPA detected low-energy ion spectral peaks (LISPs) that fell into two categories: isotropic and field aligned. Isotropic LISPs were detected most frequently in the 0200-0500 magnetic local time (MLT) sector and relatively high levels of Kp. They always were detected in the company of >10 keV plasma sheet electrons and appeared in one or, at most, two LEPA energy channels. Field-aligned LISPs were evenly distributed over the sampled MLT sector and magnetic activity levels. They could be either bidirectional or monodirectional. They too were detected along with plasma sheet electrons whose spectra may or may not contain significant fluxes at energies {ge} 10 keV. Although some field-aligned LISPs were detected in one or two energy channels, others were quite spread in energy. Isotropic LISPs are interpreted as signatures of CRRES charging. Field-aligned LISPs cannot be due to charging. On the basis of other measurements at geostationary orbit, the authors interpret them as being of ionospheric origin. Their detection in the postmidnight sector suggests that they were initially accelerated perpendicular to (ion conics) rather than along (ion beams) the Earth`s magnetic field. 23 refs., 3 figs., 1 tab.
- OSTI ID:
- 227126
- Journal Information:
- Journal of Geophysical Research, Vol. 100, Issue A10; Other Information: PBD: 1 Oct 1995
- Country of Publication:
- United States
- Language:
- English
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