HR: 0800h
AN: SA31A-04    [Abstracts]
TI: Simultaneous Analysis of COSMIC Ionospheric Occultations and Airglow Images During Periods of Equatorial Spread F
AU: * Miller, E S
EM: esmiller@uiuc.edu
AF: University of Illinois at Urbana-Champaign, 1308 W Main St, Urbana, IL 61801, United States
AU: Makela, J J
EM: jmakela@uiuc.edu
AF: University of Illinois at Urbana-Champaign, 1308 W Main St, Urbana, IL 61801, United States
AU: Syndergaard, S
EM: ssy@ucar.edu
AF: UCAR, COSMIC Project Office P.O. Box 3000, Boulder, CO 80307, United States
AB: GPS-LEO radio occultation measurements are an important source of atmospheric and ionospheric state parameter data, particularly in locations not served by incoherent scatter or MST radars. Classical radio occultation theory invokes the assumption of locally spherical symmetry through the Abel transform to invert the refractive index profile, and thus the electron density and other parameters. While it is well-known that departures from spherical symmetry near the tangent point are detrimental to this inversion, the effects of horizontal gradients have not been studied in detail. One source of severe localized electron density gradients are depletions associated with equatorial spread F. These depletions are readily imaged from the ground as dark regions in otherwise bright recombination airglow emissions. Ground-based imaging of these emissions can provide a two-dimensional map of the horizontal gradients in the ionosphere. Thus, exploiting the field-aligned nature of the depletions, airglow images may be extruded along the geomagnetic field to form an approximate three- dimensional representation of the depleted flux tubes. In this study, we present several cases from the COSMIC mission illustrating the effects of horizontal gradients on occultation ray paths that traverse depleted flux tubes. Depleted flux tubes are identified using a narrow-field airglow imager at Cerro Tololo, Chile, operating in a field- aligned viewing geometry.
DE: 2415 Equatorial ionosphere
DE: 2439 Ionospheric irregularities
DE: 2494 Instruments and techniques
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly