1. A cloud of gas, liquid, aerosols, or particles originating from within a planet. The term is most commonly used for the gas and aerosols emitted by a volcano that drift downwind. The plumes above the erupting volcanoes of Io are the largest and most spectacular such examples, some rising to 280 km altitude and depositing material 500 km from the vent. The plumes seen rising from the surface of Triton by Voyager 2 appear to be from geyser-like eruptions.
2. A ray-like feature seen in the Sun’s atmosphere. See coronal plume.