TEC values obtained from TOPEX satellite were compared with the International Reference Ionospher... more TEC values obtained from TOPEX satellite were compared with the International Reference Ionosphere (IRI) 2001 model estimates. The present work also shows results of the IRI model with the option of a new topside electron density distribution (NeQuick model). TOPEX TEC measurements, which include years of high and middle to low solar activity (2000 and 2004), were analyzed by binning the region covered by the satellite (±66°) every five degrees of modip. In general, there is good agreement between IRI predictions and Topex measurements. Cases with large disagreements are observed at low and high latitudes during high solar activity. Comparing the model predictions using the default IRI2001 model and the NeQuick topside option show that the default IRI 2001 version represents the observed data in a more realistic way, but appears to be less reliable at high and low latitudes in some cases.
Tsunami warning signs in the ionosphere ? Thanks to the advent of satellite ionospheric monitorin... more Tsunami warning signs in the ionosphere ? Thanks to the advent of satellite ionospheric monitoring techniques, a few were non-ambiguously observed. We report new observations related to the recent Samoan tsunami. We detected ionospheric disturbances in the hours following the earthquake. We extracted short time Total Electron Content (TEC) variations from data recorded by permanent Global Positioning System (GPS) stations located in the whole Pacific area. At near field, a gravito-acoustic signal is clearly detected within 15 minutes after the seismic rupture. These coseismic ionospheric perturbations are now commonly detected after strong earthquakes through monitoring of TEC derived by GPS data. For underwater earthquakes, this kind of observation can improve the understanding of tsunami generation. At far field, using a dense GPS network in Hawaii, we imaged a 10 to 15 minutes periodic signal around 6 hours after the earthquake, propagating between 150 and 200 m/s to the North-Ea...
Journal of Atmospheric and Solar-Terrestrial Physics, 2008
ABSTRACT The NeQuick electron density model of the ionosphere is designed for trans-ionospheric p... more ABSTRACT The NeQuick electron density model of the ionosphere is designed for trans-ionospheric propagation applications. The model topside has been revised on the basis of ISIS 2 topside sounder profiles, producing a new formulation of its empirical shape parameter. Comparisons between experimental slant TEC data and values modelled using both versions of NeQuick topside showed that in general we have obtained a distinct improvement. However, during some months of the year and at low latitudes, the new topside formulation does not produce improvements on the slant TEC estimates. We discuss the likely reasons for this behaviour including assessment of merits and shortcomings of the ISIS 2 data in low latitudes. The topside sounder on Intercosmos 19 satellite extensively sounded the equatorial region during a period of high solar activity, which was less covered by ISIS 2. This paper presents comparisons of NeQuick and topside sounders profiles at low latitudes using Intercosmos 19 satellite data.
TEC values obtained from TOPEX satellite were compared with the International Reference Ionospher... more TEC values obtained from TOPEX satellite were compared with the International Reference Ionosphere (IRI) 2001 model estimates. The present work also shows results of the IRI model with the option of a new topside electron density distribution (NeQuick model). TOPEX TEC measurements, which include years of high and middle to low solar activity (2000 and 2004), were analyzed by binning the region covered by the satellite (±66°) every five degrees of modip. In general, there is good agreement between IRI predictions and Topex measurements. Cases with large disagreements are observed at low and high latitudes during high solar activity. Comparing the model predictions using the default IRI2001 model and the NeQuick topside option show that the default IRI 2001 version represents the observed data in a more realistic way, but appears to be less reliable at high and low latitudes in some cases.
Tsunami warning signs in the ionosphere ? Thanks to the advent of satellite ionospheric monitorin... more Tsunami warning signs in the ionosphere ? Thanks to the advent of satellite ionospheric monitoring techniques, a few were non-ambiguously observed. We report new observations related to the recent Samoan tsunami. We detected ionospheric disturbances in the hours following the earthquake. We extracted short time Total Electron Content (TEC) variations from data recorded by permanent Global Positioning System (GPS) stations located in the whole Pacific area. At near field, a gravito-acoustic signal is clearly detected within 15 minutes after the seismic rupture. These coseismic ionospheric perturbations are now commonly detected after strong earthquakes through monitoring of TEC derived by GPS data. For underwater earthquakes, this kind of observation can improve the understanding of tsunami generation. At far field, using a dense GPS network in Hawaii, we imaged a 10 to 15 minutes periodic signal around 6 hours after the earthquake, propagating between 150 and 200 m/s to the North-Ea...
Journal of Atmospheric and Solar-Terrestrial Physics, 2008
ABSTRACT The NeQuick electron density model of the ionosphere is designed for trans-ionospheric p... more ABSTRACT The NeQuick electron density model of the ionosphere is designed for trans-ionospheric propagation applications. The model topside has been revised on the basis of ISIS 2 topside sounder profiles, producing a new formulation of its empirical shape parameter. Comparisons between experimental slant TEC data and values modelled using both versions of NeQuick topside showed that in general we have obtained a distinct improvement. However, during some months of the year and at low latitudes, the new topside formulation does not produce improvements on the slant TEC estimates. We discuss the likely reasons for this behaviour including assessment of merits and shortcomings of the ISIS 2 data in low latitudes. The topside sounder on Intercosmos 19 satellite extensively sounded the equatorial region during a period of high solar activity, which was less covered by ISIS 2. This paper presents comparisons of NeQuick and topside sounders profiles at low latitudes using Intercosmos 19 satellite data.
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