Browsing by Author "Ilma, Ronald"

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    Local ionospheric empirical model based on Jicamarca incoherent scatter radar data
    (Instituto Geofísico del Perú, 2010) Ilma, Ronald
    Diapositivas presentadas en el Encuentro Científico Internacional, ECI-2010, celebrado en Lima, Perú.
    Palabras clave:IonosphereRadarHigh atmosphere
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    Modeling the IRI topside profile using scale heights from ground-based ionosonde measurements
    (Elsevier, 2004) Reinisch, Bodo W.; Huang, Xue-Qin; Belehaki, Anna; Shi, Jian-Kui; Zhang, Man-Lian; Ilma, Ronald
    Ionograms present a new data resource for an effort to improve the IRI topside profiles. Ground-based ionograms measure the Chapman scale height at the P2 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 and height-integrated 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, the difference being attributed to the plasmasphere. It is suggested to use the scale height HT, routinely measured by a large number of digisondes around the globe, for the construction of a topside electron density profile that could become an option in the IRI model. To quickly establish a large database for HT, it would be useful to take advantage of the autoscaled HT values. A comparison of monthly medians using automatically and manually determined HT values is made. Direct calculation of HT from the bottomside IRI profile defined by B0, B1, D1, NmF2, and hmF2 using the same extrapolation technique suggests an alternate path to an estimate of the topside profile.
    Palabras clave:Topside profileScale heightIonosphere
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    Modeling the low-latitude ionospheric electron density and plasma turbulence in the November 2004 storm period
    (Elsevier, 2010-03) Retterer, J. M.; Ilma, Ronald; Kelley, M. C.; Chau Chong Shing, Jorge Luis; Valladares, C. E.; Gentile, L. C.; Groves, K.
    The storm period of 8–12 November 2004 offers an opportunity for insight into the phenomena of low-latitude ionospheric structure during geomagnetically disturbed times because of the strength of the disturbances, the timing of the storms, and the instrumentation that was operating during the interval. We will take advantage of these factors to model the ambient ionosphere and the plasma turbulence responsible for radio scintillation within it, using the AFRL low-latitude ambient/turbulent ionospheric model and the storm-time model features described in the companion paper [Retterer, J.M., Kelley, M.C., 2009. Solar-wind drivers for low-latitude ionospheric models during geomagnetic storms. J. Atmos. Solar-Terr. Phys., this issue]. The model plasma densities show very good agreement with the densities measured by the Jicamarca ISR as well as with the total electron content (TEC) measured by the Boston College South American chain of GPS receivers. The detection by the radar of coherent returns from plasma turbulence match well the times of predicted ionospheric instability. The predicted geographic extent of the occurrence of equatorial plasma bubbles was matched by DMSP satellite observations and our forecasts of scintillation strength were validated with measurements of S4 at Ancon and Antofagasta by stations of the AFRL SCINDA network.
    Palabras clave:Low-latitude ionosphereModelingPlasma structure and instability