The E-layer, or E-region, is a part of the Earth's ionosphere, located approximately 90 to 150 kilometers above the surface. It plays a crucial role in radio wave propagation, as it reflects certain frequencies back to the Earth, allowing for long-distance communication. The E-layer is formed by the ionization of atmospheric gases due to solar radiation. This layer is influenced by solar activity, such as solar flares and coronal mass ejections, which can enhance its ionization levels. Variations in the E-layer can affect navigation systems and radio signals, making it an important area of study for scientists and engineers working in telecommunications and space weather forecasting.