Variations in Ionospheric Parameters Associated With the 20–21 May 2012 Annular and 21 August 2017 Total Solar Eclipses

This study investigates the ionospheric effects of the annular solar eclipse (20–21 May 2012) and total solar eclipse (21 August 2017) across midlatitude stations, analyzing critical parameters: F2‐layer critical frequency (foF2), peak height (hmF2), and total electron content (TEC). Using ionosonde data and geomagnetic indices, we isolated eclipse‐driven perturbations by comparing observations with quiet‐day baselines. Both eclipses induced significant reductions in foF2 and TEC (~30%–38% during totality and 15%–25% during annularity), with pre‐eclipse transient enhancements, which might be attributed to traveling ionospheric disturbances (TIDs). The total eclipse caused a notable hmF2 uplift (~20 km), whereas the annular eclipse showed negligible changes, reflecting different thermospheric cooling magnitudes for eclipses with different magnitude and obscuration rates. Stations under higher obscuration (e.g., Idaho, 100%) experienced stronger depletions, supporting the role of eclipse magnitude. Recovery times for foF2 (1–3 h) exceeded TEC restoration, which might be due to transport‐driven F2‐layer dynamics. Although noticeable variation is observed on foF2 and TEC parameters, their magnitudes are found to vary with local time, latitude, and obscuration rate. These findings emphasize the ionosphere′s layered sensitivity to solar forcing and have implications for GNSS and communication systems vulnerable to TEC fluctuations.