HR: 08:15h
AN: SA21B-02    [Abstracts]
TI: Ionospheric Superstorms: Polarization Terminator Effects in the Atlantic Sector
AU: * Foster, J C
EM: jfoster@haystack.mit.edu
AF: MIT Haystack Observatory, Route 40, Westford, MA 01886, United States
AU: Erickson, P J
EM: perickson@haystack.mit.edu
AF: MIT Haystack Observatory, Route 40, Westford, MA 01886, United States
AB: A combination of the stormtime penetration electric fields, the effect of the reduced magnetic field strength in the South Atlantic magnetic anomaly, and the geographic distortion of the magnetic field in the Atlantic sector contribute to the characteristics of the low-latitude polarization electric fields at the sunset terminator. This combination of effects leads to a strong localized enhancement of TEC at low-mid latitudes in the American sector during ionospheric superstorms. At dusk, the low-latitude polarization electric field effects begin on magnetic field lines when the E region at either end goes into darkness. We define the polarization terminator (PT) to be the locus of points at a given altitude for which the E-region shadow height at either end of the magnetic field line equals 100 km. Electric fields associated with the charge build-up in the conductivity-gradient region due to the effects of winds or penetration electric fields are directed perpendicular to the PT and increase in magnitude as the PT is approached from the dayside. The particular configuration of the magnetic field in the Atlantic sector creates a preferred longitude/Universal Time sector (western atlantic/ 21 UT) for the build-up of enhanced TEC on field lines inside the dusk plasmapause. The electric fields associated with the PT sweep up the plasmas of the equatorial anomaly crests and redistribute it into the mid-latitude SAPS channels, forming the high total content storm enhanced density (SED) plumes observed during strong storms in the American sector. This effect is most pronounced for northern hemisphere summer conditions, as experienced during the July 15/16, 2000 superstorm.
DE: 2411 Electric fields (2712)
DE: 2415 Equatorial ionosphere
DE: 2437 Ionospheric dynamics
DE: 7949 Ionospheric storms (2441)
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting