The Characteristics and Simulation of Sporadic E Layers in Ascending and Descending Phases of the Solar Cycle at Mid-Latitude Stations

Abstract

Most of the attention was paid to the correlation between Sporadic E (Es) layers and solar activity, and conflicting conclusions were obtained in previous research. For the first time, we analyze the influence of solar activity on the number of Es layer traces (Es layers with a certain duration and intensity), the lifetime and descent velocity of the descending Es layer traces, and the results have been explained using simulation based on windshear theory and Lomb-Scargle (LS) spectral analysis. A statistical analysis of Es layers observed in ascending (2010–2012) and descending (2016–2018) phases of the solar cycle is presented at three different mid-latitude stations of Kuming (25.5°N, 103.8°E), Lanzhou (36.1°N, 103.9°E) and Urumqi (43.8°N, 87.6°E) in China region. The observation results indicate that the occurrence rate, height distribution and the number of the Es layer traces are all influenced by solar activity, indicating that they are negatively correlated with solar activity. The simulation, spectral analysis, and observations reveal that the lifetime and descent velocity of the descending Es layer traces are mainly modulated by semidiurnal and diurnal tides, but are less affected by solar activity. The predominant oscillations of the Es layer are identified using LS spectral analysis. The spectral analysis reveals that the modulation of diurnal tide waves on Es layers dominates at lower mid-latitudes, and that of semidiurnal tide waves dominates at higher latitudes. The results also confirm the modulation of planetary waves on Es layers at different mid-latitudes.