HR: 0800h
AN: SA51A-1119    [Abstracts]
TI: Analysis and Simulation of E Region Neutral Structures Within the Pre and Post Midnight Diffuse Aurora
AU: * Parish, H F
EM: helen@atmos.ucla.edu
AF: University of California Los Angeles, Dept. of Atmospheric and Oceanic Sciences, 405, Hilgard Avenue, Los Angeles, CA 90095-1565 United States
AU: Lyons, L R
EM: larry@atmos.ucla.edu
AF: University of California Los Angeles, Dept. of Atmospheric and Oceanic Sciences, 405, Hilgard Avenue, Los Angeles, CA 90095-1565 United States
AB: Rocket release experiments within the pre and post midnight substorm recovery phase diffuse aurora reveal strong vertical structure and large shears in the E region neutral winds. Wind velocities up to 200 m/s around 115 km altitude, were observed on the dawn side during the ARIA (Atmospheric Response in Aurora) and earlier rocket campaigns, and even larger winds up to 400 m/s, around 130 km altitude, were measured on the dusk side. Observed wind magnitudes appear to have a dependence on geomagnetic activity level, but recent work suggests that tidal variations in the background winds play an important role in generating the observed structures on both the dawn and dusk sides. The relative importance of different forcing mechanisms in generating the strong vertical structure, and how this may be affected by changes in the orientation of the background winds relative to the aurora, such as those which may be produced by changes in IMF orientation, are not well known. The enhanced auroral precipitation and electric fields associated with magnetic storms and substorms are likely to have significant effects on the neutral thermosphere, locally and at lower latitudes, and the sensitivity of the E region neutral response to strong auroral forcing, for varying background winds and tides, is investigated. Propagating tides, which may have important effects on high latitude E region wind structures, are highly variable, and the effects of changing the time at which tidal forcing is introduced relative to the time when strong auroral forcing begins, for varying geomagnetic conditions, are not well known. Simulations have been performed using a 3-dimensional, high resolution, limited area model, where parameters measured at dawn and dusk provide auroral forcing inputs for the model, and global background winds and tides are given by the CTIP (Coupled Thermosphere Ionosphere Plasmasphere) model. The relative importance of different forcing mechanisms, the sensitivity to changes in the electric field and ion density enhancement for varying background winds orientation, and the sensitivity to changes in the timing of the introduction of background winds have been examined, in order to understand the formation of the observed E region structures.
DE: 0310 Airglow and aurora
DE: 3369 Thermospheric dynamics (0358)
DE: 3389 Tides and planetary waves
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005