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The 630 nm MIG and the vertical neutral wind in the low latitude nighttime thermosphereIt is shown that large negative divergences (gradients) in the horizontal neutral wind in the equatorial thermosphere can support downward neutral winds in excess of 20 m/s. With attention to the meridional and vertical winds only, the pressure tendency equation is used to derive the expression U(sub z0) approximately equals (Partial derivative U(sub y)/Partial derivative y)H for the vertical wind U(sub z0) at the reference altitude for the pressure tendency equation; H is the atmospheric density scale height, and (Partial derivative U(sub y)/Partial derivative y) is the meridional wind gradient. The velocity gradient associated with the Meridional Intensity Gradient (MIG) of the O((sup 1)D) emission (630 nm) at low latitudes is used to estimate the vertical neutral wind in the MIG region. Velocity gradients derived from MIG data are about 0.5 (m/s)/km) or more, indicating that the MIG region may contain downward neutral winds in excess of 20 m/s. Though direct measurements of the vertical wind are scarce, Fabry-Perot interferometer data of the equatorial F-region above Natal, Brazil, showed downward winds of 30 m/s occurring during a strong meridional wind convergence in 1982. In-situ measurements with the WATS instrument on the DE-2 satellite also show large vertical neutral winds in the equatorial region.
Document ID
19950032357
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Herrero, F. A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Meriwether, J. W., Jr.
(Clemson Univ. Clemson, SC, United States)
Date Acquired
August 16, 2013
Publication Date
January 15, 1994
Publication Information
Publication: Geophysical Research Letters
Volume: 21
Issue: 2
ISSN: 0094-8276
Subject Category
Geophysics
Accession Number
95A63956
Distribution Limits
Public
Copyright
Other

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