Hands up if you’ve ever seen Steve. No, not the chap living down the road, but Steve the winter sky phenomenon. First spotted by auroral photographers in 2016, “Steve” is a purple band of light, sometimes accompanied by green lines, nicknamed “picket-fences”.
Although Steve shares similarities with auroras – the glowing coloured lights visible from high latitudes during winter months – latest research shows that Steve is something quite different. Analysing photos of Steve taken from different locations, and using the stars in the background as markers, scientists have shown that Steve sits at between 130km and 270km altitude, while the picket fence is between 95km and 150km.
Compared with conventional auroras, Steve has a wider range of wavelengths, is longer and thinner, doesn’t hang around for as long and appears in areas further south than a typical aurora.
Auroras are formed by charged particles disturbing Earth’s magnetic field, but Steve’s distinctly different shape and behaviour suggests that his origins lie in some unusual chemistry involving very hot ionised gas. It’s likely Steve has been around for eons, but mis-identified as aurora until now. Most of us are unlikely to see him, but thankfully he has now been captured on film – Chasing Steve.