The F layer, also known as the F region, is a part of the Earth's ionosphere, located approximately 150 to 1,000 kilometers above the Earth's surface. It is characterized by a high concentration of free electrons and ions, which are created by solar radiation. This layer plays a crucial role in radio wave propagation, allowing long-distance communication by reflecting certain frequencies back to the Earth's surface. The F layer is divided into two sub-layers: the F1 layer and the F2 layer. The F1 layer is typically present during the day, while the F2 layer is more prominent at night. Variations in the F layer's density and height can affect satellite communications and GPS accuracy, making it an important area of study in space weather research.