Thanks to scientists, citizen scientists, ground-based imagers and ESA’s magnetic field Swarm mission, this purple streak of light in the night sky has been discovered. Originally thought to be a ‘proton arc’, this strange feature has been called Steve. While there is still a lot to learn about Steve, the electric field instrument carried on the Swarm mission has measured it. Flying through Steve, the temperature 300 km above Earth’s surface jumped by 3000°C and the data revealed a 25 km-wide ribbon of gas flowing westward at about 6 km/s compared to a speed of about 10 m/s either side of the ribbon.
Read full story: When Swarm met Steve