Nudging Earth's ionosphere with radio waves helps us learn more about it, study shows

Between 50 and 1,000 kilometers above our heads is the ionosphere, a layer of Earth's upper atmosphere consisting of charged particles: ions (atoms that have gained or lost a negatively charged electron) and loose electrons. The ionosphere alters the path of electromagnetic waves that reach it, including radio and GPS signals, so studying it is helpful for understanding communication and navigation systems.