A magnascopic storm was a type of astronomical phenomena.
In 2370, a magnascopic storm occurred while the USS Enterprise-D was exploring the Mekorda sector. Lieutenant Commander Data later speculated that the storm was responsible for the emergent circuit nodes appearing on the ship. (TNG: "Emergence")
The Star Trek Encyclopedia (4th ed., vol. 2, p. 11) defined "magnascopic storm" as an electromagnetic spatial distortion.