Plasma sheet boundary layer
Journal Article
·
· J. Geophys. Res.; (United States)
The plasma sheet boundary layer is a temporally variable transition region located between the magnetotail lobes and the central plasma sheet. We have made a survey of these regions by using particle spectra and three-dimensional velocity-space distributions sampled by the ISEE 1 LEPEDEA. Ion composition measurements obtained by the Lockhead ion mass spectrometers indicate that ionospheric ions play a crucial role in magnetotail dynamics. Eleven crossings from the lobes to the central plasma sheet taken at various local times and levels of geomagnetic activity are analyzed in detail. The average ratios of He/sup +//H/sup +/, He/sup + +//H/sup +/, and O/sup +//H/sup +/ are not significantly different between the plasma sheet boundary layer and central plasma sheet. Densities and temperatures intermediate between the central plasma sheet and lobes are oberved in the plasma sheet boundary layer although bulk flow speeds there are typically enhanced. Counter-streaming ion beams are often observed in the plasma sheet boundary layer at energies of approx.1 keV/q to >45 keV/q. Intense antisunward-flowing beams of ionospheric origin at E/q of <1 kV are often seen in the tail lobes, the plasma sheet boundary layer, and, infrequently, in the central plasma sheet. Such beams are not commonly observed in the central plasma sheet, which is characterized by hotter and more isotropic ion and electron distributions. Our samples of ion distributions in the plasma sheet boundary layer frequently show an evolution of distribution functions from highly anisotropic single beams or counter-streaming beams toward the more isotropic distributions typical of the hot component of the central plasma sheet.
- Research Organization:
- Department of Physics and Astronomy, University of Iowa
- OSTI ID:
- 6468235
- Journal Information:
- J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 89:A3; ISSN JGREA
- Country of Publication:
- United States
- Language:
- English
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