HR: 09:45h
AN: SA41A-07    [Abstracts]
TI: Modeling of Equatorial Anomaly Development and Collapse at Dusk Observed by TIMED/GUVI Over Indian Longitudes
AU: * Basu, S
EM: sbasu@bu.edu
AF: Boston Uiversity, 725 Commonwealth Avenue, Boston, MA 02215, United States
AU: Basu, S
EM: santimay@aol.com
AF: Air Force Research Laboratory, 29 Randolph Road, Hanscom AFB, MA 01731, United States
AU: Huba, J
EM: Joseph.Huba@nrl.navy.mil
AF: Naval Research Laboratory, Overlook Avenue, S.W., Washington, DC 20375, United States
AU: Makela, J
EM: jmakela@uiuc.edu
AF: University of Illinois, University Road, Urbana, IL 61821, United States
AU: Ray, S
EM: ashik_paul@rediffmail.com
AF: University of Calcutta, 92 Acharya Prafulla Ch. Road, Calcutta, 700009, India
AU: Groves, K
EM: Keith.Groves@hanscom.af.mil
AF: Air Force Research Laboratory, 29 Randolph Road, Hanscom AFB, MA 01731, United States
AB: The GUVI instrument on NASA's TIMED satellite acquires images of 135.6-nm emission in the Earth's ionosphere/thermosphere system. The brightness of the GUVI images is approximately proportional to the square of the electron density and, as such, the images can be used to monitor the equatorial F region ionization anomaly. The intensity and separation of these bands are controlled by the equatorial E-B drift and the meridional neutral wind. Further, the collapse of the anomaly has been linked to the suppression of irregularities causing scintillations. The SAMI3, another model of the ionosphere, has been utilized to model the evening collapse of the anomaly in the Indian longitude sector where measurements of TEC, scintillations and estimates of the daytime vertical drifts are available. Preliminary results from SAMI3 show that the collapse of the anomaly at dusk can be simulated by a reduction of the vertical drift, and its reversal in mid-afternoon in agreement with the drift estimates from magnetometer observations. Introduction of neutral winds into SAMI3 reproduces the dusk behavior of TEC at low latitude stations in India. While preliminary results from SAMI3 provide some insights into the day-to-day variation of scintillations, much further work is necessary, particularly on the relative effects of the pre-reversal enhancement of the vertical drifts, time of reversal, neutral winds and the conductivity in the E-region on the generation and suppression of instabilities. We hope these modeling efforts will eventually lead to the isolation of a unique set of drivers that control large and small scale plasma structuring.
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2435 Ionospheric disturbances
DE: 2437 Ionospheric dynamics
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 3369 Thermospheric dynamics (0358)
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly