HR: 0800h
AN: SA51B-1131    [Abstracts]
TI: Modeling shear flow and postsunset stability in the equatorial F region ionosphere
AU: * Hysell, D
EM: dlh37@cornell.edu
AF: Earth and Atmospheric Science, Cornell University, Ithaca, NY 14853 United States
AU: Larsen, M
EM: mlarsen@hubcap.clemson.edu
AF: Physics and Astronomy, Clemson University, Clemson, SC 29634 United States
AU: Swenson, C
EM: charles.swenson@usu.edu
AF: Electrical and Computer Engineering, Utah State University, Logan, UT 84322 United States
AU: Wheeler, T
EM: tfw1@psu.edu
AF: Electrican Engineering, Penn State University, University Park, PA 16802 United States
AB: Sounding rocket and Altair radar data taken during the NASA EQUIS-II campaign on Kwajalein in August, 2004, are incorporated into a computational model of the electrodynamics of the low-latitude ionosphere. The purpose is to understand and quantify sources of the strong shear flow observed in the bottomside F region around and after sunset and to assess its influence on postsunset stability and the production of equatorial spread F. Possible sources of shear include 1) zonal electric fields on flux tubes with significant Hall conductivity, as are responsible for driving the equatorial electrojet, 2) zonal winds on flux tubes with significant Pedersen conductivity, as drive the E and F region dynamos, 3) vertical winds, a largely unknown quantity, and 4) vertical boundary currents forced from above or below the flux tube in question. The model solves for the electrostatic potential in three dimensions as a function of the background conductivity, background electric field, and the winds. We do not assume equipotential field lines but instead solve for the potential exactly using a multigridded solver. Shear flow may destabilize the postsunset ionosphere through a collisional shear instability related to electrostatic Kelvin Helmholtz [ Hysell and Kudeki, 2004]. Assessing the viability of the instability requires us to identify and rank in importance the sources of the shear.
DE: 2411 Electric fields (2712)
DE: 2415 Equatorial ionosphere
DE: 2437 Ionospheric dynamics
DE: 2439 Ionospheric irregularities
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005