Northern Lights Steve: The rare phenomenon not related to aurora borealis and how to spot it

Last night a spectacular display illuminated parts of the UK as the Aurora Borealis dominated the night sky - despite the fireworks for Bonfire Night. The natural display was seen as far south as Stonehenge in Wiltshire and provided a magnificent sight for those lucky enough to have caught it. 

However, there was one other light that stargazers noticed - peculiarly known as Steve. Standing for Strong Thermal Emission Velocity Enhancement, Steve has been noticed by auroral photographers for decades but it is not part of the Aurora Borealis display.

Northern Lights & Steve explained

Steve is plasma. More specifically, Steve is an atmospheric optical phenomenon appearing as a purple and green light ribbon in the sky. Analysis reveals that the phenomenon is caused by a 25 km (16 mi) wide ribbon of hot plasma at an altitude of 450km (280 mi), with a temperature of 3,000C and flowing at a speed of 6 km/s (3.7 mi/s). 

Steve observations are thought to have been recorded as early as 1705 with notations resembling phenomenon existing in some observations from 1911 to the 1950s by Carl Størmer (a Norwegian mathematician and astronomer). However, members of a Facebook group, Alberta Aurora Chasers, named it, attributed it to a proton aurora, and began calling it a "proton arc".

However, when physics professor Eric Donovan from the University of Calgary saw their photographs he said proton auroras are not visible. Between when he correlated the time and location of the phenomenon with Swarm satellite and one of the Alberta Aurora Chaser photographers, Song Despins who provided GPS coordinates from Vimy, Alberta, Donovan could link the data to identify the phenomenon. 

Steve has only been spotted in the presence of an aurora, but it does not appear regularly. The phenomenon appears as a very narrow arc extending for hundreds or thousands of miles, aligned east–west. It generally lasts for twenty minutes to an hour, and has been seen in the United Kingdom, Canada, Alaska, northern US states, Australia, and New Zealand. 

Why is it called Steve?

The name is inspired by the film, Over the Hedge (2006). One of the aurora watchers, photographer Chris Ratzlaff suggested the name of the light could be taken after the scene in the film when the characters in the movie give the name to a hedge that appears overnight, in order to make it seem more benign. 

In 2016, during a meeting of the American Geophysical Union in December 2016, Robert Lysak suggested using a backronym of "Steve" for the phenomenon making it stand for "Strong Thermal Emission Velocity Enhancement".