The sky over New Zealand was lit up by a red light. Newly released images show that over the next half hour, an amateur skywatcher observed that arcs before his eyes into one of Earth's most puzzling atmospheric mysteries.
STEVE, short for "strong thermal velocity enhancement," is an atmospheric phenomenon first described in 2018, after amateur Aurora chasers saw a small stream of purple light in the sky over northern Canada. The multi-colored glow that appears at high latitudes when solar particles collide with atoms is not an Aurora. STEVE was a different phenomenon that was completely unknown to science.
STEVE appears as a single ribbon of light that stabs straight upward for hundreds of miles, unlike the northern lights, which tend to shimmer in broad bands of green, blue or red light. It is accompanied by a broken green line of lights. In a part of the atmosphere known as the subauroral region, where charged solar particles are not likely to hurt, STEVE and his picket fence friend appear much lower in the sky.
For the first time, research published in the journal Geophysical Research Letters has linked STEVE to a subauroral structure.
The authors compared the New Zealand skywatcher's March 2015 footage with satellite observations and data from an all-sky imager at Mount John Observatory. The researchers were able to see STEVE's appearance that night.
The sky show began with a blood-red SAR arcs that flew over New Zealand. Satellite data shows that the arcs appearance coincides with a strong storm of charged solar particles in the atmosphere.
The red arcs gradually gave way to the signature purple streak of STEVE, which slashed through the sky in almost the exact same spot. The green picket fence structure shimmered into view. According to the researchers, this is the first time that all three structures have appeared in the sky at the same time.
The researchers wrote in the new study that the phenomena are distinct from the Auroras, as their optical signatures seem to be triggered by extreme thermal and kinetic energy in Earth's atmosphere.
Satellites show that the night's storm may have been a factor in the parade of sky lights.
A fast- moving jet of charged particles appeared in the sky during the storm. Subauroral ion drift is a stream of hot, fast particles in the sky. The heat and speed of the stream increased when STEVE appeared.
According to the researchers, a "plausible generation mechanism" for STEVE could be the interaction between these fast- moving ion streams and nitrogen molecule in the subauroral zone.
More observations of STEVE, from citizen scientists and professional researchers alike, are needed to further pin down the mystery of the phenomenon.
It was originally published on Live Science
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