Local Time and Seasonal Variations in the Electron Density at the Ionospheric F2-Layer Maximum with Wave Disturbances under Low Solar Activity Conditions

Resumo

Regular and quasi-periodic local time and seasonal variations in the electron density in the maximum of the ionospheric F2 layer during low solar activity in 2016 are analyzed. System spectral analysis of temporal variations in the electron density in the range of 30–180 min is based on windowed Fourier transform, adaptive Fourier transform, and wavelet transform. In all seasons, the ionospheric F2 layer is dominated by oscillation with a period of 70–120 min, an amplitude of ΔN_a ≈ (2–10) × 10¹⁰ m^–3, and a relative amplitude of \({{\Delta {{N}_{a}}} \mathord{\left/ {\vphantom {{\Delta {{N}_{a}}} {\bar {N}}}} \right. \kern-0em} {\bar {N}}}\) ≈ 0.20–0.70. The duration of this oscillation varied from 6 to 17 h depending on the season. The amplitude of oscillations with other periods is significantly smaller. It has been confirmed that the regular local time and seasonal variations in the electron density in the F2-layer maximum are fully consistent with the existing views on physicochemical processes in the ionosphere. The main regularities in the behavior of quasi-periodic variations in the electron density have been revealed.