Browsing by Author "Huang, X."

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    Formation of an F3 layer in the equatorial ionosphere: A result from strong IMF changes
    (Elsevier, 2007-07) Paznukhov, V. V.; Reinisch, B. W.; Song, P.; Huang, X.; Bullet, T. W.; Veliz, Oscar
    We analyzed ionospheric observations made with digisondes in Jicamarca, Ramey, Wallops Island, Ascension Island, and Kwajalein Island during the major magnetic storm of November 9–10, 2004, which was associated with rapid interplanetary magnetic field (IMF) Bz changes. The strongest ionospheric responses to the southward IMF Bz turning were observed at the dip equator at Jicamarca where during the magnetic disturbance a dramatic F2 peak density depletion occurred at around 15:00 local time, accompanied by a fast upward motion of the plasma. In this process, an additional ionospheric layer, the F3 layer, formed with peak densities NmF3 exceeding NmF2. This observation may be considered evidence of an equatorial plasma fountain enhancement caused by the magnetic field disturbance. Responses were observed in a large range of latitudes and local times. The best indicator of the responses appears to be the peak height of the F layer, since competing processes determine the peak densities. The observed responses at low latitude locations in the morning and dusk sectors pose challenges to the simple penetrating electric field model because the upward motion is inconsistent with the E×B drift associated with a dawn–dusk electric field. Clear responses in the Jicamarca local time sector occurred at latitudes as high as 28, at Ramey, Puerto Rico. This latitude range appears to be beyond the range of the flux tube corresponding to the 900 km F3 layer peak height at Jicamarca, indicating a more extended uplifting of flux tubes.
    Palabras clave:F3 layerEquatorial plasma fountainElectron density profiles
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    Using scale heights derived from bottomside ionograms for modelling the IRI topside profile
    (Copernicus Publications, 2005-05) Reinisch, B. W.; Huang, X.; Belehaki, A.; Ilma, R.
    Groundbased ionograms measure the Chapman scale height HT at the F2-layer peak that is used to construct the topside profile. After a brief review of the topside model extrapolation technique, comparisons are presented between the modeled profiles with incoherent scatter radar and satellite measurements for the mid latitude and equatorial ionosphere. The total electron content TEC, derived from measurements on satellite beacon signals, is compared with the height-integrated profiles ITEC from the ionograms. Good agreement is found with the ISR profiles and with results using the low altitude TOPEX satellite. The TEC values derived from GPS signal analysis are systematically larger than ITEC. It is suggested to use HT , routinely measured by a large number of Digisondes around the globe, for the construction of the IRI topside electron density profile.
    Palabras clave:ExtrapolationIncoherent scattering radarIonosphere