A plasma streamer was a stream of plasma between two stars of a binary system. Plasma streams created ionized distortion fields surrounding them, greatly reducing the efficacy of sensors, transporters, and even tractor beams.
In 2369, the USS Enterprise-D was sent to the Igo sector to investigate the loss of contact with the USS Yosemite, a science vessel sent to remotely observe the stream. The Enterprise discovered that quasi-energy microbes lived within the streamer's distortion field. (TNG: "Realm of Fear")