Research on Ionospheric F Layer Characteristics During the 24th Solar Cycle at Kunming

The ionosphere, which is ionized by solar and cosmic radiation, is a part of the atmosphere that extends approximately 60 to 1000km from the surface. As an important component of the Earth's space environment, variations in the ionosphere have a significant impact on electronic information systems, potentially leading to disruptions in shortwave communications and increased errors in satellite navigation systems. Kunming is located on the southeast side of the Qinghai-Tibet Plateau with a large altitude gradient. Meanwhile, it is also situated in the north peak region of the equatorial ionization anomaly (EIA), resulting in complex and unique characteristics of ionospheric variation in the Kunming region. In this paper, we investigate the diurnal, seasonal, and solar cycle variations of the critical frequency and the bottom height of the F layer by utilizing the observation data of the 24th solar activity cycle from Kunming ionosonde station. The results provide significant insights into researching ionospheric variations and upper-lower atmospheric coupling mechanisms.