Plasma drift
A plasma drift was a nebula-like interstellar phenomenon. 

A large plasma drift moved through the Talaxian system when Neelix was a child, blocking out the stars and moons for months. ()

In 2372, the  entered a plasma drift almost half a sector long, to hide from a Vidiian-controlled star system. This was considered large for a plasma drift. Upon leaving the drift, they encountered some subspace turbulence that was in fact a divergence field. ()

de: Plasmaströmung
Celestial objects