Abstract
The dependence of the local annual asymmetry index AI on solar activity has been analyzed based on daily data on the noon values of the F2-layer maximum electron density, NmF2, at the Boulder and Hobart ionospheric stations for 1963–2002. The AI index characterizes the relative difference in the total electron density NmF2 in January and July for a given pair of stations. The weighted-average index of geomagnetic activity ap(τ) at τ = 0.8 was used for the analysis. Low (ap(τ) < 9) and moderate (9 < ap(τ) < 20) geomagnetic activities were identified. It was found for the first time that for low geomagnetic activity, the AI index increases from 0.08 during low solar activity to 0.11–0.12 during moderately high and high solar activity. The AI index for moderate geomagnetic activity is higher (by ΔAI = 0.04–0.05) than that for low geomagnetic activity, which is almost independent of the solar activity level. The AI index for NmF2 median values increases from 0.08 during low solar activity to 0.15–0.16 during high solar activity, which indicates the important role of geomagnetic activity in the dependence of this index on solar activity. A qualitative interpretation of these patterns is given.
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5. ACKNOWLEDGMENTS
The authors are grateful to the World Data Center for Solar-Terrestrial Physics, Great Britain, for the foF2 data from Boulder and Hobart stations and solar activity indices (http://www.ukssdc.ac.uk/wdcc1/) and the World Data Center for Geomagnetism, Japan, for the Ap index data (http://wdc.kugi.kyoto-u.ac.jp/).
Funding
The study was funded by the Russian Foundation for Basic Research as part of the scientific project no. 20-05-00050.
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Translated by M. Chubarova
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Deminov, M.G., Deminova, G.F. Dependence of the Local Index of Annual Asymmetry for NmF2 on Solar Activity. Geomagn. Aeron. 61, 227–233 (2021). https://doi.org/10.1134/S0016793221020055
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DOI: https://doi.org/10.1134/S0016793221020055