Ion Storm

An ion storm is an astronomical phenomenon caused by a supernova. Although referred to as storms, they are in fact wind cells of natural gas ejected from the upper atmosphere of supernovae. When a star explodes, it typically expels this gas at speeds of up to several percent of the speed of light, driving a radially-expanding shockwave out into space. This gas is ionised on account of the supernova's production of copious amounts of ultraviolet light and cosmic ray spallation.

An ion storm forms an expanding bubble of ionised gas around the supernova’s epicentre once the warm, expanding wind cells encounter the cold, interstellar gases of neighbouring space. This bubble can become an insurmountable barrier to spacecraft because contact with high densities of ionised gas can interfere with spacecraft’s electrical systems. Long-distance communication and accurate, safe computer-assisted FTL travel through ion storms are untenable as electrical signals cannot penetrate them. Eventually, the bubble expands to such a large diameter that the density of the ionised gas becomes diminished and the ion storm dissipates. The duration of time this takes is dependent on the size of the supernova and therefore the volume of ionised gas it expels.

Large swathes of Necraal territory were rendered untraversable by ion storms, a factor that played a role during the Necraal Schism.