Variability of foF2 in the equatorial ionosphere

Bilitza, D.; Obrou, O. K.; Adeniyi, J.O.; Oladipo, O.A.

doi:10.1016/j.asr.2004.08.004

Cited by 70 publications

(83 citation statements)

References 5 publications

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“…In addition, the differences of our results from Obrou et al (2003) may partly come from the longitudinal structure of h m F 2 . The observations given above are in accord with the findings reported by Bilitza et al (2004b) using data collected at the two stations, Korhogo and Ouagadougou during low, moderate and high solar activity years of 1995 and 1985, 1998 and 1993, and 2000 and 1991, respectively; to examine variability of f o F 2 at the two stations. In a comparative analysis between f o F 2 observations and IRI model at low latitude station, Ibadan,Nigeria (7.4 • N, 3.9 • E; 5 • S dip angle), Oyekola (2011) found IRI model to be larger than the measured f o F 2 in June from 1900-0500 LT and September from 1900-2300 LT.…”

Section: Discussionsupporting

confidence: 79%

Equatorial vertical plasma drifts and the measured and IRI model-predicted F 2-layer parameters above Ouagadougou during solar minimum

Oyekola¹

2012

Earth Planet Sp

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In this paper, hourly median value of ionosonde measurements: peak height F 2 -layer (h m F 2 ), F 2 -layer critical frequency ( f o F 2 ) and propagation factor M(3000)F 2 made at near-equatorial dip latitude, Ouagadougou, Burkina Faso (12• N, 1.5 • W; dip: 1.5• N) and relevant F 2 -layer parameters: thickness parameter (B o ), electron temperature (T e ), ion temperature (T i ), total electron content (TEC) and electron density (N e ) (at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial electrodynamics on the diurnal structure of F 2 -layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. It is demonstrated that the month-by-month morphological patterns between vertical E × B drifts and F 2 -layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F 2 -layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-B o , IRI-T e and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Examination of the association between measured f o F 2 , h m F 2 and M(3000)F 2 illustrates consistent much more smaller correlation coefficients with no systematic linkage.

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Section: Discussionsupporting

confidence: 79%

Equatorial vertical plasma drifts and the measured and IRI model-predicted F 2-layer parameters above Ouagadougou during solar minimum

Oyekola¹

2012

Earth Planet Sp

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“…However, Kazimirovski (2002) stated that the TEC also generates significant day-to-day variations during magnetically quiet periods due to the thermospheric dynamics caused by different types of atmospheric disturbances from the lower atmosphere. Earlier observations have confirmed that the day-to-day TEC variability caused by thermospheric dynamics in the equatorial latitudes does not usually exceed 20% (Forbes et al, 2000;Rishbeth and Mendillo, 2001;Bilitza et al, 2004). Our result shows that the maximum values of the pre-earthquake daytime positive anomalies exceeded 20%.…”

Section: Analysis Of the Ionospheric Variations Before The 26 Decembesupporting

confidence: 75%

Ionospheric variations before some large earthquakes over Sumatra

Hasbi

Ali

Misran

2011

Nat. Hazards Earth Syst. Sci.

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Abstract. The paper investigates the ionospheric variations before some large earthquakes that occurred during [2004][2005][2006][2007] in Sumatra using GPS and CHAMP data. The TEC shows the occurrence of positive and negative anomalies detected within a few hours to 6 days before the earthquakes. These anomalies mostly occur during the daytime hours between 4 and 17 LT. The TEC anomalies are mostly consistent with the CHAMP satellite electron density data. The electron density analysis over the 28 March 2005 earthquake epicenter shows that an equatorial anomaly modification took place a few days before the event. The modification took shape in the form of crest amplification during the daytime. The comparison between the TEC and electron density measurements during very quiet geomagnetic conditions is shown to be a useful indicator of a forthcoming earthquake.

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“…More and more applications, however, require a description of the day-to-day variations. In some cases an estimate of the expected range of variability is all that is needed and there is an IRI effort underway to include a quantitative description of ionospheric variability in IRI in the form of the monthly standard deviation (Araujo-Pradere et al 2004Bilitza et al 2004). A more accurate description of the changes from day to day requires the use of real-time data and of updating or assimilation techniques to combine IRI with these data and in the process produce the Real-Time IRI (IRI-RT).…”

Section: Real-time Irimentioning

confidence: 99%

The International Reference Ionosphere 2012 – a model of international collaboration

Bilitza

Altadill²,

Zhang

et al. 2014

J. Space Weather Space Clim.

554

347

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The International Reference Ionosphere (IRI) project was established jointly by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) in the late sixties with the goal to develop an international standard for the specification of plasma parameters in the Earth's ionosphere. COSPAR needed such a specification for the evaluation of environmental effects on spacecraft and experiments in space, and URSI for radiowave propagation studies and applications. At the request of COSPAR and URSI, IRI was developed as a data-based model to avoid the uncertainty of theory-based models which are only as good as the evolving theoretical understanding. Being based on most of the available and reliable observations of the ionospheric plasma from the ground and from space, IRI describes monthly averages of electron density, electron temperature, ion temperature, ion composition, and several additional parameters in the altitude range from 60 km to 2000 km. A working group of about 50 international ionospheric experts is in charge of developing and improving the IRI model. Over time as new data became available and new modeling techniques emerged, steadily improved editions of the IRI model have been published. This paper gives a brief history of the IRI project and describes the latest version of the model, IRI-2012. It also briefly discusses efforts to develop a real-time IRI model. The IRI homepage is at http://IRImodel.org.

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Variability of foF2 in the equatorial ionosphere

Cited by 70 publications

References 5 publications

Equatorial vertical plasma drifts and the measured and IRI model-predicted F 2-layer parameters above Ouagadougou during solar minimum

Equatorial vertical plasma drifts and the measured and IRI model-predicted F 2-layer parameters above Ouagadougou during solar minimum

Ionospheric variations before some large earthquakes over Sumatra

The International Reference Ionosphere 2012 – a model of international collaboration

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