- Disturbance of the Earth’s magnetic field by the arrival of charged particles from the Sun during periods of exceptional solar activity. Geomagnetic storms can seriously disrupt of radio communications.
- A large-scale, often worldwide, disturbance of the geomagnetic field. Such storms are characterized by a sudden onset, and their effects may last from a few minutes to several days. geomagnetic storms are usually caused by solar flares, and affect radio frequency communications. Also called magnetic storm.