Impact of Solar Activity on Short Period Ionospheric Oscillations

We study the characteristics of the Earth's ionosphere short period oscillations over multiple years spanning two solar maxima. We analyze the ground-based Global Navigation Satellite System vertical total electron content (TEC) at locations close to the magnetic equator in South America and India, as well as in North America, from January 2000 through December 2017. We use Morlet wavelets to spectrally analyze the ionospheric TEC variability over solar cycles 23 and 24 and find that the ionosphere exhibits dominant modes of oscillation at the same periods (5–6 days) as planetary waves. Interestingly, these oscillations manifest as 2–3 TECU fluctuations, are enhanced during spring, and show strong covariations with the 10.7 cm solar flux. We hypothesize that, once these short-period oscillations are formed, the solar activity drives their strength with distinct enhancements during solar maxima and pronounced suppressions at the transition from the solar cycle 23 to 24.