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ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa
CURRENT PROBLEMS IN REMOTE SENSING OF THE EARTH FROM SPACE

  

Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2026, V. 23, No. 2, pp. 385-397

Estimation of the total electron content distribution correlation scale in the European region using a variogram approach based on GNSS radio sounding data

I.A. Pavlov 1, 2 , A.M. Padokhin 1, 2 
1 Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS, Troitsk, Moscow, Russia
2 Lomonosov Moscow State University, Moscow, Russia
Accepted: 10.02.2026
DOI: 10.21046/2070-7401-2026-23-2-385-397
The paper presents a method for estimating the correlation scale of the ionospheric Total Electron Content (TEC) distribution using Global Navigation Satellite System (GNSS) radio sounding data. The method uses data obtained from the Madrigal database to construct empirical variograms of TEC residuals relative to the 27-day median distribution of electron density. The correlation scale was determined by fitting the parameters of a Gaussian variogram model to best match the obtained empirical variograms. Analysis of data from 2018, a year characterized by low solar and geomagnetic activity, showed that in the European region, the TEC correlation scale exhibits seasonal variability, increasing from ~1000 km in winter months to 2000–4000 km in summer, which agrees well with the variability of the Regional Electron Content (REC). From analysis of variogram surfaces, a significant anisotropy of the TEC correlation scale was revealed associated with the directions of magnetic field and neutral wind at the F2 layer peak altitudes. The research results have practical significance for the tasks of adapting ionospheric models and assimilating TEC data for the purpose of forecasting radio wave propagation conditions, as well as for understanding the dynamics of ionospheric processes at midlatitudes.
Keywords: ionosphere, GNSS, correlation scale, variogram
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