Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsa72b0531p&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #SA72B-0531
Physics
0358 Thermosphere: Energy Deposition, 2704 Auroral Phenomena (2407), 2788 Storms And Substorms, 3369 Thermospheric Dynamics (0358), 3384 Waves And Tides
Scientific paper
Measurements within the substorm recovery phase dawn sector diffuse aurora reveal features which are not well understood. Strong neutral winds are seen within the postmidnight diffuse aurora in measurements from the series of ARIA (Atmospheric Response in Aurora) campaigns, which show a great deal of vertical structure and large vertical shears. The ARIA observations consistently show a peak in the wind magnitude between around 110 km and 120 km, which has not been well explained, and strong shears below the peak. Some of these shears are unstable, with a Richardson number < 0.25. A 3-D high resolution model which has been developed recently at UCLA, has been used to perform simulations to try to understand the poorly explained phenomena observed in the ARIA measurements. Model simulations show that large zonal and meridional winds can be produced in the region of the postmidnight diffuse aurora, and a wind maximum is produced in the 110 to 120 km altitude range, within the same height range as the maxima found in the ARIA observations, using auroral forcing alone. When sufficiently high vertical resolution is used, using auroral forcing parameters within the range of observations, the region below the peak is found to be unstable, with a Richardson number < 0.25. When simulations are performed with auroral forcing parameters based on measurements from the ARIA I campaign, and background winds and tides are introduced from the CTIP (Coupled Thermosphere Ionosphere Plasmasphere) model, the basic features of the vertical structure of the ARIA I wind measurements are reproduced. The results of simulations suggest that tidal forcing, especially of higher order tidal modes, is important in producing the observed vertical structure. The 115 km peak is likely produced by a combination of auroral and tidal forcing processes. The vertical structure of the winds is sensitive to the phases of the tidal modes. Improvements in the ability of the model to simulate the observations from the ARIA campaign may be due to the use of the 3-dimensional rather than a 2-dimensional high resolution model.
Jones Patricia P.
Lyons Larry
Parish Helen F.
Walterscheid Richard
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