Understanding ‘Steve’
The world’s physicists are scrambling to identify a phenomenon that aurora-watchers are seeing with increasing frequency.
UNLIKE MOST space news you receive via these pages, this issue’s column sits firmly in the ‘people-powered research’ province. And, intriguingly, it’s about a phenomenon that no-one really understands yet.
Watching the northern and southern polar lights (aurora borealis and aurora australis) has become more and more popular with citizen scientists.This has been fuelled as much by digital cameras capable of stunning time-lapse videos as by the increasing ease of travel to good vantage points. Aurora-watchers are now equally at home in southern Tasmania or far-northern Sweden.
Auroral displays occur when subatomic solar particles collide with atoms of Earth’s upper atmosphere, exciting them into a colourful frenzy. Watching them is highly addictive, and dedicated aurora observers scan the internet for satellite-based forecasts of activity.The light and colour patterns are well studied and mostly well understood – particularly since the International Space Station first became a unique vantage point for aurorae 17 years ago.
But in recent years, something new has been increasingly spotted: narrow ribbons of purplish light, sometimes right across the sky, and apparently independent of the rest of the display. Some aurora-watchers have termed these mysterious features ‘proton arcs’, although science tells us that aurorae caused by protons (as distinct from electrons) from the Sun should be virtually invisible. A more likely interpretation is that they are SAR(Stable Auroral Red) arcs, which have been reported since the 1970s as looking as if they’re detached from an auroral display.
You have to hand it to citizen scientists, though. Faced with an apparently nameless but real phenomenon, they’ve followed characters of the 2006 children’s movie Over the Hedge, who named an animal they didn’t know ‘Steve’. So, with the celestial Steve rapidly becoming an internet sensation among aurora followers, understanding it has become a priority for the world’s space physicists.