Four large-scale field-aligned current systems in the dayside high- latitude region

S. Ohtani, T. A. Potemra, P. T. Newell, L. J. Zanetti, T. Iijima, M. Watanabe, L. G. Blomberg, R. D. Elphinstone, J. S. Murphree, M. Yamauchi, J. G. Woch

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Abstract

A system of four current sheets of large-scale field-aligned currents (FACs) was discovered in the data set of simultaneous Viking and DMSP-F7 crossings of the dayside high-latitude region. This paper reports four examples of this system that were observed in the prenoon sector. The flow polarities of FACs are upward, downward, upward, and downward, from equatorward to poleward. The lowest-latitude upward current is flowing mostly in the CPS precipitation region, often overlapping with the BPS at its poleward edge, and is interpreted as a region 2 current. The pair of downward and upward FACs in the middle of the structure are collocated with structured electron precipitation. The precipitation of high-energy (>1 keV) electrons is more intense in the lower-latitude downward current sheet. The highest-latitude downward flowing current sheet is located in a weak, low-energy particle precipitation region, suggesting that this current is flowing on open field lines. Simultaneous observations in the postnoon local time sector reveal the standard three-sheet structure of FACs, sometimes described as region 2, region 1, and mantle (referred to the midday region 0) currents. A high correlation was found between the occurrence of the four FAC sheet structure and negative interplanetary magnetic field (IMF) BY We discuss the FAC structure in terms of three types of convection cells: the merging, viscous, and lobe cells. During strongly negative IMF BY two convection reversals exist in the prenoon sector; one is inside the viscous cell, and the other is between the viscous cell and the lobe cell. This structure of convection flow is supported by the Viking electric field and auroral UV image data. Based on the convection pattern, the four FAC sheet structure is interpreted as the latitudinal overlap of midday and morning FAC systems. We suggest that the four-current sheet structure is common in a certain prenoon local time sector during strongly negative IMF BY.

Original languageEnglish
Pages (from-to)137-153
Number of pages17
JournalJournal of Geophysical Research
Volume100
Issue numberA1
DOIs
Publication statusPublished - Jan 1995

Fingerprint

field aligned currents
polar regions
current sheets
magnetic fields
Magnetic fields
interplanetary magnetic fields
sectors
cells
convection
electrons
Electrons
tropical regions
Merging
lobes
energy
electric field
magnetic field
Electric fields
particle precipitation
convection cells

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

Ohtani, S., Potemra, T. A., Newell, P. T., Zanetti, L. J., Iijima, T., Watanabe, M., ... Woch, J. G. (1995). Four large-scale field-aligned current systems in the dayside high- latitude region. Journal of Geophysical Research, 100(A1), 137-153. https://doi.org/10.1029/94JA01744

Four large-scale field-aligned current systems in the dayside high- latitude region. / Ohtani, S.; Potemra, T. A.; Newell, P. T.; Zanetti, L. J.; Iijima, T.; Watanabe, M.; Blomberg, L. G.; Elphinstone, R. D.; Murphree, J. S.; Yamauchi, M.; Woch, J. G.

In: Journal of Geophysical Research, Vol. 100, No. A1, 01.1995, p. 137-153.

Research output: Contribution to journalArticle

Ohtani, S, Potemra, TA, Newell, PT, Zanetti, LJ, Iijima, T, Watanabe, M, Blomberg, LG, Elphinstone, RD, Murphree, JS, Yamauchi, M & Woch, JG 1995, 'Four large-scale field-aligned current systems in the dayside high- latitude region', Journal of Geophysical Research, vol. 100, no. A1, pp. 137-153. https://doi.org/10.1029/94JA01744
Ohtani, S. ; Potemra, T. A. ; Newell, P. T. ; Zanetti, L. J. ; Iijima, T. ; Watanabe, M. ; Blomberg, L. G. ; Elphinstone, R. D. ; Murphree, J. S. ; Yamauchi, M. ; Woch, J. G. / Four large-scale field-aligned current systems in the dayside high- latitude region. In: Journal of Geophysical Research. 1995 ; Vol. 100, No. A1. pp. 137-153.
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