An ion storm (also called an ionic storm or ionic front) is a type of magnetic storm which contains ionically charged particles, traveling at thousands of kilometers an hour. Both planetary and spaceborne ion disturbances can intensify to the point where navigation is dangerous, and transporter use all but impossible. At higher levels ion storms can damage or destroy spacecraft.
Ion storms are prevalent in the Denorios belt and have been since at least the 22nd century. In the Bajoran year 9174, Akorem Laan's lightship was caught in an ion storm there and was severely damaged. (DS9: "Explorers", "Accession")
The Kalandra star system has many ion storms. In 2375, Captain Benjamin Sisko and General Martok expressed their concerns the storms would reveal the Federation Alliance starships to the Dominion. (DS9: "The Emperor's New Cloak")
In the 23rd century, Template:ShipClass starships were equipped with an ion pod, allowing the starships to acquire data in conditions that defeated their conventional sensor platforms. Starships traversing ion storms were buffeted by the storms "weather" effects and subjected to tremendous hull pressures and stress. Starfleet used the measurement of a storm's relative effect on the ship as a supplementary data point to judge the intensity of an ion storm, and hazards it posed. Minor but noticeable "natural vibrations" were labeled Force-2 on an incremental scale. Above Force-7, the starship was at increased risk and subject to the captain's call for red alert status. (TOS: "Court Martial")
Later in 2267, the interference of an ion storm around Halkan homeworld caused a transporter malfunction that exchanged Captain Kirk and three of his officers with their counterparts from an alternate reality, placing them in the mirror universe. (TOS: "Mirror, Mirror")