ionosfäärästä

The ionosphere is a region of Earth's upper atmosphere, extending from about 60 kilometers (37 miles) to 1,000 kilometers (620 miles) above the surface. It is characterized by the presence of a significant number of ions and free electrons, which are created when solar radiation, particularly ultraviolet rays and X-rays, strikes neutral atmospheric molecules and atoms, knocking electrons free. This process is called ionization. The density of ions and electrons varies considerably with altitude, time of day, season, and solar activity.

The ionosphere plays a crucial role in radio wave propagation. Its ionized layers act like a mirror, reflecting certain frequencies of radio waves back to Earth, allowing for long-distance communication. Different layers within the ionosphere, such as the D, E, and F layers, have distinct ionization densities and affect radio waves differently. The D layer, present during the day, absorbs most low-frequency radio waves, while the E and F layers reflect higher frequencies. The ionosphere also influences satellite communication and GPS signals. Phenomena like auroras, the northern and southern lights, occur in the ionosphere when charged particles from the sun interact with atmospheric gases.