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Interhemispheric asymmetry of the high-latitude ionospheric convection patternThe assimilative mapping of ionospheric electrodynamics technique has been used to derive the large-scale high-latitude ionospheric convection patterns simultaneously in both northern and southern hemispheres during the period of January 27 to 29, 1992. When the interplanetary magnetic field (IMF) B(sub z) component is negative, the convection patterns in the southern hemisphere are basically the mirror images of those in the northern hemisphere. The total cross-polar cap potential drops in the two hemispheres are similar. When B(sub z) is positive and absolute value of B(sub y) greater than B(sub z), the convection configurations are mainly determined by B(sub y) and they may appear as normal 'two-cell' patterns in both hemispheres much as one would expect under southward IMF conditions. However, there is a significant difference in the cross-polar-cap potential drop between the two hemispheres, with the potential drop in the southern (summer) hemisphere over 50% larger than that in the northern (winter) hemisphere. As the ratio of absolute value of B(sub y)/B(sub z) decreases (less than one), the convection configuration in the two hemispheres may be significantly different, with reverse convection in the southern hemisphere and weak but disturbed convection in the northern hemisphere. By comparing the convection patterns with the corresponding spectrograms of precipitating particles, we interpret the convection patterns in terms of the concept of merging cells, lobe cells, and viscous cells. Estimates of the ' merging cell' potential drops, that is, the potential ascribed to the opening of the dayside field lines, are usually comparable between the two hemispheres, as they should be. The 'lobe cell' provides a potential between 8.5 and 26 kV and can differ greatly between hemispheres, as predicted. Lobe cells can be significant even for southward IMF, if absolute value of B(sub y) greater than the absolute value of B(sub z). To estimate the potential drop of the 'viscous cells,' we assume that the low-latitude boundary layer is on closed field lines. We find that this potential drop varies from case to case, with a typical value of 10 kV. If the source of these cells is truly a viscous interaction at the flank of the magnetopause, the process is likely spatially and temporally varying rather than steady state.
Document ID
19950029593
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lu, G.
(National Center for Atmospheric Research, Boulder, CO United States)
Richmond, A. D.
(National Center for Atmospheric Research, Boulder, CO United States)
Emery, B. A.
(National Center for Atmospheric Research, Boulder, CO United States)
Reiff, P. H.
(Rice Univ. Houston, TX, United States)
Beaujardiere, O. De LA
(SRI, Menlo Park, CA United States)
Rich, F. J.
(Hanscom Air Force Base MA, United States)
Denig, W. F.
(Hanscom Air Force Base MA, United States)
Kroehl, H. W.
(National Geophysical Data Center Boulder, CO, United States)
Lyons, L. R.
(The Aerospace Corp. Los Angeles, CA, United States)
Ruohoiemi, J. M.
(Johns Hopkins Univ. Laurel, MD, United States)
Date Acquired
August 16, 2013
Publication Date
April 1, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: A4
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A61192
Funding Number(s)
CONTRACT_GRANT: NASA ORDER W-17384
CONTRACT_GRANT: NSF ATM-91-20072
CONTRACT_GRANT: NAG5-1099
CONTRACT_GRANT: NSF ATM-90-03860
CONTRACT_GRANT: NSF ATM-91-03440
CONTRACT_GRANT: NAGW-1655
CONTRACT_GRANT: NSF-92-02795
Distribution Limits
Public
Copyright
Other

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