What Is STEVE and Why Isn't It an Aurora?

STEVE is a mysterious purple ribbon of light that appears in the night sky and reaches temperatures of 3,000°C, but despite its aurora-like appearance, it’s an entirely different atmospheric phenomenon that scientists still don’t fully understand.

The Accidental Discovery by Citizen Scientists

The discovery of STEVE reads like a modern fairy tale of citizen science. Around 2015-2016, amateur photographers in the Alberta Aurora Chasers Facebook group began capturing images of an unusual purple ribbon streaking across the night sky. Unlike the familiar green curtains of aurora borealis, this phenomenon appeared as a narrow, east-west oriented band of light.

The photographers playfully named it “STEVE” after a hedge character from the animated film “Over the Hedge.” Scientists later created a backronym to match: Strong Thermal Emission Velocity Enhancement. This grassroots discovery highlights how citizen scientists can spot patterns that escape academic notice, even when the data has existed for decades.

The Shocking Temperature Mystery

When the European Space Agency directed a satellite directly through STEVE, the measurements were startling. The purple ribbon burns at approximately 3,000°C—more than half the surface temperature of the Sun. Even more puzzling, the air just centimeters away from this plasma ribbon remains at only a few hundred degrees Celsius.

This extreme temperature differential defies easy explanation and distinguishes STEVE from traditional auroras, which result from solar particles interacting with Earth’s magnetic field. STEVE appears to be driven by entirely different mechanisms that atmospheric scientists are still working to understand.

Hidden in Plain Sight for Forty Years

Perhaps the most remarkable aspect of STEVE’s story is that satellite sensors had been detecting this phenomenon since the 1970s. For roughly four decades, the data existed in scientific archives, but nobody realized this atmospheric anomaly was also visible to the naked eye. It took amateur photographers with cameras and keen observation skills to connect the dots between ground-based visual observations and satellite measurements.

The Dual Nature of STEVE

STEVE became even more intriguing when scientists confirmed in 2019 that it’s actually two distinct phenomena. The purple ribbon itself is one component, while the green “picket fence” streaks that sometimes appear alongside it represent a completely separate mechanism. Both components remain poorly understood, with researchers still debating the underlying physics that creates these spectacular displays.

This dual nature further separates STEVE from conventional auroras and suggests that our atmosphere holds more mysteries than previously imagined. The phenomenon challenges existing models of atmospheric physics and continues to generate new research questions.

Ongoing Scientific Investigation

Today, STEVE serves as a bridge between citizen science and academic research. Professional atmospheric physicists now collaborate with amateur photographers to gather more observations and data about when and where STEVE appears. This partnership demonstrates how modern scientific discovery can emerge from unexpected sources and highlights the value of careful observation by dedicated enthusiasts.

The mystery of STEVE reminds us that even in our well-studied atmosphere, new phenomena await discovery by anyone willing to look up at the night sky with curiosity and attention to detail.