Magnioactivity is a scientific effect dealing with interactions of energy, magnetism, and radiation.

A magnioactive storm could disrupt the functions of 23rd century Federation technology, such as shuttlecraft and transporters. Conversely, a magnioactive surge could favorably affect conditions for such devices to operate effectively. Magnioactive conditions existed on and around the planet Klatoor.

A magnioactive storm once threatened to set down upon a Starfleet landing party from the Federation starship USS Enterprise as they traveled between the plateaus of Belga and Amsha seeking components to build a cyclonic generator from the five plateau-dwelling tribes of the Klatoor natives. The landing party also had a chance to observe a favorable magnioactive surge while traveling between the plateaus of Shema and Gnass. (TOS - Star Trek Annual 1978 comic: "... Wild Goose Chase!")