HR: 16:45h
AN: SA14A-06    [Abstracts]
TI: Longitudinal Variability of Plasma Structuring in the Equatorial and Middle Latitudes During Magnetically Quiet and Disturbed Times - A Global M-I-T Coupling Issue
AU: * Basu, S
EM: sbasu@bu.edu
AF: Boston University, Center for Space Physics 725 Commonwealth Avenue, Boston, MA 02215 United States
AU: Basu, S
EM: santimay@aol.com
AF: Air Force Research Laboratory, AFRL/VSBXI, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AU: Valladres, C
EM: valladar@bc.edu
AF: Boston College Institute for Scientific Research, 140 Commonwealth Avenue, Chestnut Hill, MA 02467 United States
AU: McDonald, S
EM: sarah.mcdonald@nrl.navy.mil
AF: Naval Research Laboratory, 4555 Overlook Avenue, Washigton, DC 20375 United States
AU: Groves, K
EM: Keith.Groves@hanscom.af.mil
AF: Air Force Research Laboratory, AFRL/VSBXI, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AB: The synoptic global views of the equatorial anomaly provided by the GUVI instrument on TIMED has shed new light on the longitudinal variability of equatorial plasma structure first studied with the OGO - 6 satellite almost 30 years ago (Basu et al., Radio Sci., 1976). The eastward electric field at the magnetic equator during the post-sunset hours drives the equatorial ionosphere unstable, generates plasma bubbles and causes scintillations. This eastward electric field also causes a resurgence of the equatorial ionization anomaly providing a large scale ionization distribution as a function of latitude. The GUVI images of 135.6 nm emissions are able to image the variability of the anomaly peaks as a function of longitude while chains of GPS ground stations have provided information regarding the variability of both the total electron content and scintillations. A marked longitudinal variability of the anomaly peaks even on magnetically quiet days probably indicates the influence of other poorly known "drivers", such as complex neutral dynamics. The relationship between the large scale plasma density gradients, small-scale structuring and the requirement for a seeding mechanism for plasma instabilities is far from resolved. During magnetic storms, penetration of electric fields of magnetospheric origin provides another degree of complexity, facilitating the growth of instabilities in certain longitude sectors and inhibiting them in others, depending on the interplay of storm time and local time effects. In addition, during severe magnetic storms plumes of greatly enhanced density and associated small-scale irregularities are seen at middle latitudes, primarily over the continental US (Basu et al., GRL, 2005). Such plasma structuring, seen at middle and equatorial latitudes under high solar flux conditions, cause severe disruption of satellite communication and GPS navigation systems. A comprehensive I/T Storm Probe Mission, augmented by sensors to define magnetospheric inputs, is necessary for an understanding of these phenomena so that predictive space weather models can be developed to minimize societal impacts.
DE: 2415 Equatorial ionosphere
DE: 2439 Ionospheric irregularities
DE: 2443 Midlatitude ionosphere
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2788 Storms and substorms
SC: SPA-Aeronomy [SA]
MN: 2005 Joint Assembly