Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation
Russian Academy of Sciences
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Model of the equatorial anomaly in foF2 from the Intercosmos-19 satellite data for high solar activity

Karpachev A.T., IZMIRAN, e-mail: karp@izmiran.ru
Pustovalova L.V., IZMIRAN, e-mail: pustoval@izmiran.ru

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An empirical model of the equatorial anomaly (EA) in foF2 is constructed. The basis of the model is the data of the Intercosmos-19 satellite, obtained in 1979-1981 for quiet conditions under high solar activity (F10.7 ~200). The model reproduces latitudinal, longitudinal, diurnal, and seasonal variations in foF2 within ±70°of the geomagnetic inclination.
In any season, EA according to the model begins to develop from ~08 LT. A well-developed EA under high solar activity exists until 02 LT and is completely absent at 04-06 LT. The distribution of foF2 in the EA region for different seasons and local time hours has been studied in detail and corrected in previous papers [Karpachev, 2018, 2020, 2021a], therefore the model reproduces the longitudinal variations in foF2 more adequately than the IRI model, especially at the equator and over the oceans. As a result, the model reproduces latitudinal variations in foF2 also more adequately, in particular, it describes the structure of the Weddell Sea anomaly (WSA) more exactly than IRI.
The greatest discrepancies between the new model and IRI-2016 for any season (month) are observed in the Pacific longitudinal sector, where there are few ground stations (see also [Karpachev, 2021b]). The discrepancies are large at midnight, since the decay of EA in IRI begins earlier than according to satellite data, and in the morning at 06 LT, since according to IRI, the growth of foF2 begins much earlier than sunrise. The foF2 model is presented in the form of foF2 tables for all months after 2 hours of local time 00, 02 ...22 LT. The foF2 values are presented with a step of 5 in latitude and 30 in longitude. The values of foF2 for any moment of LT, latitude and longitude are determined using interpolation. A new model in the form of a program is installed on the IZMIRAN website: https://www.izmiran.ru/ionosphere/eia/. This program allows to calculate the values of foF2 at each point, longitudinal, latitudinal, diurnal and seasonal variations in foF2, as well as the distribution of foF2 for fixed moments of LT and UT time.


  • Karpachev, A.T., 2018. Diurnal and longitudinal variations of the structure of Equatorial Anomaly during equinoxes according to the Intercosmos-19 satellite data. Geomagnetism and Aeronomy. 58(3), 407419. doi: 10.1134/S0016793218030076
  • Karpachev, A.T., 2020. Variations in the structure of the Equatorial Anomaly during the summer solstice according to the Interkosmos-19 satellite. Geomagnetism and Aeronomy. 60(2), 224235. doi: 10.1134/S0016793220020061
  • Karpachev, A.T., 2021a. Diurnal and longitudinal variations of the Equatorial Anomaly for December solstice according to the Interkosmos-19 satellite. Geomagnetism and Aeronomy, 61(1), 2943. doi: 10.31857/S0016794021010065.
  • Karpachev A.T. 2021b. Equatorial anomaly according to the Interkosmos-19 data and IRI model: A comparison // Advances in Space Research, 67. 32023212. doi:10.1016/j.asr.2021.01.053.

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