Abstract
A comparison between two of the most used scintillation models and experimental data is presented. The experimental data have been derived from a GPS scintillation monitor developed at Cornell University and placed in Tucuman (Argentina), under the peak of the anomaly. The models used (GISM and WBMOD) have been run for the geophysical conditions corresponding to the measurements. The comparison is done by subdividing the information on the basis of an ionospheric grid of 5° ×5° surface square boxes. The comparison has been performed for several local times, from 18 LT until 04 LT. Here, only a few cases of particular interest are shown. The goal is to understand if the models are able to forecast actual scintillation morphology (from the satellite navigation systems point of view) and if they could be used to yield an estimate of scintillation effects on satellite navigation systems.
Highlights
When traversing drifting ionospheric irregularities, a radio wave experiences fluctuations in its amplitude and phase: the fluctuation characteristics depend on the radio frequency, magnetic and solar activity, time of day, season of the year and magnetic latitude of the observation point in the case of satellite to ground links.Nowadays, one of the most important fields where as complete as possible knowledge of ionospheric scintillation effects is needed is that of satellite based navigation systems
Such an approach does not take into account any particular navigation system characteristics and is only able to generate from experimental data global morphology of scintillation activity, as observed at a given site by means of a particular GPS receiver
The comparison between data and Global Ionospheric Scintillation Model (GISM) simulations has to be taken into account with caution, because while GISM is directly computing the most probable S4 within a given ionospheric box and during particular geophysical conditions, the experimental data are in the form of percentages of occurrence of an S4 greater than a given thresholds
Summary
When traversing drifting ionospheric irregularities, a radio wave experiences fluctuations in its amplitude and phase: the fluctuation characteristics depend on the radio frequency, magnetic and solar activity, time of day, season of the year and magnetic latitude of the observation point in the case of satellite to ground links. The classical method used to analyze scintillation data deals with average scintillation activity varying with geophysical conditions such as season and solar activity Such an approach does not take into account any particular navigation system characteristics and is only able to generate from experimental data global morphology of scintillation activity, as observed at a given site (or in a given area) by means of a particular GPS receiver. Using such an approach the actual effect of ionospheric plasma irregularities on satellite navigation operations can be assessed only to a limited extent. A validation of WBMOD has been attempted in the Southeast Asian sector (Cervera et al, 2001)
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