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The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the postmidnight sector. A combination of chemical release rocket wind measurements, instrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. We focus on the neutral wind measurements made with the rocket. The forcing was determined by running the •ssimil•ted m•pping of ionospheric electrodynamics (AMIE) •n•lysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of 00100 m s -1 developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of 00150 m s -1 developed near 115 km •titude. The large amplitude winds at the lower •ltitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tid• models, and the shear found just below the peak in the winds was nominally unstable with a Richardson number of 000.08. response of the neutral atmosphere will be especially strong in the region of diffuse aurora characteristic of the morning side. In particular, the broad spatial extent and the long-lived nature of the diffuse aurora are Paper number 95JA01346. 0148-0227/95/95 JA-01346505.00 expected to produce Lorentz forcing and Joule heating over a broad region for an extended period. The discrete aurora which typically characterize the duskside may produce stronger local forcing, but the response of the neutrals will be more limited since the spatial extent of the forcing region is small enough that the neutrals pass through the heating and acceleration regions quickly. Over the years, there have been numerous measurements of the F region neutral flow on the dawn side of the auroral oval. The Dynamics Explorer observa-17,299 17,300 LARSEN ET AL.' OBSERVATIONS OF NEUTRAL WINDS range in the mesosphere and lower thermosphere, and an instrumented rocket was used to measure the neutral composition and particle energies. In addition, an extensive set of ground-based instrumentation provided measurements of the magnetic fields and electron energies throughout the night. In this article, we will focus on the neutral wind measurements made with the chemical release rocket technique. Geophysical Conditions The chemical release experiment took place on March 3, 1992. The launch followed ...

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