Authors:
Maltseva Olga
1
and
Natalia Mozhaeva
2
Affiliations:
1
Southern Federal University, Russian Federation
;
2
Institute for Physics, Southern Federal University, Russian Federation
Keyword(s):
GPS, Total electron content TEC, Ionospheric models, Equivalent slab thickness.
Abstract:
Now the total electron content ТЕС is a key parameter characterizing conditions of the ionosphere. ТЕС is widely used for an estimation of positioning accuracy, definition of index of ionospheric storm activity. Data of TEC is very important for systems of satellite communication and navigation. The advantages of the TEC measurement are the systems of a large number of receivers, the possibility of continuous global monitoring
of the ionosphere, the availability of data on the Internet. For many systems (HF-communication, HFDF,
HFGINT) it is necessary to know the maximum density of the ionosphere NmF2 or, that is equivalent, a critical frequency foF2. To obtain NmF2, it is necessary to know the proportionality coefficient
τ=TEC/NmF2, which is the equivalent slab thickness of the ionosphere. Before occurrence of navigational
satellites, no special attention was given to this parameter and there were many inaccuracies in the papers
devoted to τ. The possibility of the global monitoring
of NmF2 with use of ТЕС, measured by navigational
satellites, makes to give the more close attention to its study. In the present paper, data of more than 50
ionospheric stations and several global maps of ТЕС are used to investigate behavior of a median τ(med) of the observational equivalent slab thickness τ(obs). Comparison of τ(med) with the equivalent slab thickness τ(IRI) of the IRI model, τ(NGM) of the Neustrelitz global model and others has shown essential differences between these values. Approaches for developing a global model of τ(med) are offered. The most amazing are following results: (1) for a large amount of stations, the use of observational TEC and τ(IRI) worsens values of foF2 compared to the initial IRI model, (2) there are no fundamental quantitative differences in the use of τ(med) for all regions of the world, (3) the IRI model and maps of TEC (in the absence of GPS receivers) for the most northern Nord station (Greenland) showed surprisingly good agreement with the experimental values of foF2.
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