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Author Burke, W. J. ♦ Machuzak, J. S. ♦ Maynard, N. C. ♦ Basinska, E. M. ♦ Erickson, G. M. ♦ Hoffman, R. A. ♦ Slavin, J. A. ♦ Hanson, W. B.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PHYSICS ♦ AURORAL ZONES ♦ CHARGED-PARTICLE PRECIPITATION ♦ IONS ♦ ORIGIN ♦ ELECTRONS ♦ PLASMA SHEET ♦ ELECTRIC FIELDS
Abstract The authors report on particles and fields observed during Defense Meteorological Satellite Program (DMSP) F9 and DE 2 crossings of the polar cap/auroral oval boundary in the evening MLT sector. Season-dependent, latitudinally narrow regions of rapid, eastward plasma flows were encountered by DMSP near the poleward boundary of auroral electron precipitation. Ten DE 2 orbits exhibiting electric field spikes that drive these plasma flows were chosen for detailed analysis. The boundary region is characterized by pairs of oppositely-directed, field-aligned current sheets. The more poleward of the two current sheets is directed into the ionosphere. Within this downward current sheet, precipitating electrons either had average energies of a few hundred eV or were below polar rain flux levels. Near the transition to upward currents, DE 2 generally detected intense fluxes of accelerated electrons and weak fluxes of ions, both with average energies between 5 and 12 keV. In two instances, precipitating ions with energies >5 keV spanned both current sheets. Comparisons with satellite measurements at higher altitudes suggest that the particles and fields originated in the magnetotail inside the distant reconnection region and propagated to Earth through the plasma sheet boundary layer. Auroral electrons are accelerated by parallel electric fields produced by the different pitch angle distributions of protons and electrons in this layer interacting with the near-Earth magnetic mirror. Electric field spikes driving rapid plasma flows along the poleward boundaries of intense, keV electron precipitation represent ionospheric responses to the field-aligned currents and conductivity gradients. The generation of field-aligned currents in the boundary layer may be understood qualitatively as resulting from the different rates of earthward drift for electrons and protons in the magnetotail`s current sheet. 45 refs., 7 figs., 2 tabs.
ISSN 01480227
Educational Use Research
Learning Resource Type Article
Publisher Date 1994-02-01
Publisher Place United States
Journal Journal of Geophysical Research
Volume Number 99
Issue Number A2


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