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The Horizontal E‐region Experiment: Evidence for inertial instability on the evening side of the auroral oval?
Author(s) -
Larsen M. F.,
Conde M. G.
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl048424
Subject(s) - zonal and meridional , meridional flow , instability , geology , geophysics , depth sounding , zonal flow (plasma) , sounding rocket , physics , atmospheric sciences , flow (mathematics) , geodesy , mechanics , astronomy , plasma , oceanography , quantum mechanics , tokamak
The Horizontal E‐region Experiment (HEX) sounding rocket experiment deployed a nearly horizontal trimethyl aluminum trail over a horizontal distance that extended more than 200 km in the meridional direction. The trail was released in the upper part of the E region between 135 and 150 km during quiet conditions with a pair of narrow auroral arcs located near the northern end of the trail. A surprising result was that large zonal winds, exceeding 250 m s −1 , were present over most of the southern half of the region in spite of the fact that the auroral forcing was very localized in meridional extent. We show that the flow was inertially unstable and suggest that the instability can account for the observed winds by significantly broadening the meridional extent of the winds generated within narrow channels in the auroral oval. The analysis focuses on the HEX observations but has broader implications since it suggests that narrow discrete arcs can generate channels of enhanced flow that are much wider than the arcs themselves. Narrow arcs can therefore have a much larger effect on the neutral circulation than would otherwise be expected.