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Title: Auroral ionospheric signatures of the plasma sheet boundary layer in the evening sector

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 producedmore » 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.« less

Authors:
; ;  [1]; ;  [2]; ;  [3];  [4]
  1. Phillips Lab., Hanscom Air Force Base, MA (United States)
  2. Boston Univ., MA (United States)
  3. Goddard Space Flight Center, Greenbelt, MD (United States)
  4. Univ. of Texas, Dallas, Richardson, TX (United States)
Publication Date:
OSTI Identifier:
28506
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research
Additional Journal Information:
Journal Volume: 99; Journal Issue: A2; Other Information: PBD: 1 Feb 1994
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; AURORAL ZONES; CHARGED-PARTICLE PRECIPITATION; IONS; ORIGIN; ELECTRONS; PLASMA SHEET; ELECTRIC FIELDS

Citation Formats

Burke, W J, Machuzak, J S, Maynard, N C, Basinska, E M, Erickson, G M, Hoffman, R A, Slavin, J A, and Hanson, W B. Auroral ionospheric signatures of the plasma sheet boundary layer in the evening sector. United States: N. p., 1994. Web. doi:10.1029/93JA02363.
Burke, W J, Machuzak, J S, Maynard, N C, Basinska, E M, Erickson, G M, Hoffman, R A, Slavin, J A, & Hanson, W B. Auroral ionospheric signatures of the plasma sheet boundary layer in the evening sector. United States. doi:10.1029/93JA02363.
Burke, W J, Machuzak, J S, Maynard, N C, Basinska, E M, Erickson, G M, Hoffman, R A, Slavin, J A, and Hanson, W B. Tue . "Auroral ionospheric signatures of the plasma sheet boundary layer in the evening sector". United States. doi:10.1029/93JA02363.
@article{osti_28506,
title = {Auroral ionospheric signatures of the plasma sheet boundary layer in the evening sector},
author = {Burke, W J and Machuzak, J S and Maynard, N C and Basinska, E M and Erickson, G M and Hoffman, R A and Slavin, J A and Hanson, W B},
abstractNote = {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.},
doi = {10.1029/93JA02363},
journal = {Journal of Geophysical Research},
number = A2,
volume = 99,
place = {United States},
year = {1994},
month = {2}
}