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Patches in the polar ionosphere: UT and seasonal dependenceThe seasonal and Universal Time (UT) dependencies of patches in the polar ionosphere are simulated using the Utah State University time dependent ionospheric model (TDIM). Patch formation is achieved by changing the plasma convection pattern in response to temporal changes in the interplanetary magnetic field (IMF) B(sub y) component during periods of southwrd IMF. This mechanism redirects the plasma flow from the dayside high-density region, which is the source of the tongue of ionization (TOI) density feature, through the throat and leads to patches, rather than a continuous TOI. The model predicts that the patches are absent at winter solstice (northern hemisphere) between 0800 and 1200 UT and that they have their largest seasonal intensity at winter solstice between 2000 and 2400 UT. Between winter solstice and equinox, patches are strong and present all day. Patches are present in summer as well, although their intensity is only tens of percent above the background density. These winter-to-equinox findings are also shown to be consistent with observations. The model was also used to predict times at which patch observations could be performed to determine the contributions from other patch mechanisms. This observational window is +/- 20 days about winter solstice between 0800 and 1200 UT in the northern hemisphere. In this observational window the TOI is either absent or reduced to a very low density. Hence the time dependent electric field mechanism considered in this study does not produce patches, and if they are observed, then they must be due to some other mechanism.
Document ID
19950053339
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sojka, J. J.
(Utah State University Logan, UT, United States)
Bowline, M. D.
(Utah State University Logan, UT, United States)
Schunk, R. W.
(Utah State University Logan, UT, United States)
Date Acquired
August 16, 2013
Publication Date
August 1, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: A8
ISSN: 0148-0227
Subject Category
Geosciences (General)
Accession Number
95A84938
Funding Number(s)
CONTRACT_GRANT: NAG5-1484
CONTRACT_GRANT: NSF ATM-93-08163
CONTRACT_GRANT: NSF ATM-89-13230
CONTRACT_GRANT: NSF ATM-93-02165
Distribution Limits
Public
Copyright
Other

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