More Aurora STEVEs or Aurora STEVElis?
'STEVE' has been described as a Strong Thermal Emission Velocity Enhancement, with NASA suggestions that these twisting filaments of ionised gas being accelerated to 4 miles per second.
Plasma STEVEs? STEVE are you plasma Birkeland filaments?
It can be spotted further south than the northern lights and is thought to be, according to a recently published paper, “an optical manifestation” of another phenomenon, the sub-auroral ion drift. Steve is a visible strip of ionised gas, travelling at 6.4km (4 miles) a second.
‘Steve’: the mystery purple aurora that rivals the northern lights | The Guardian
A glowing ribbon of purple light running east-west in the night sky has recently been observed by citizen scientists. This narrow, subauroral, visible structure, distinct from the traditional auroral oval, was largely undocumented in the scientific literature and little was known about its formation. Amateur photo sequences showed colors distinctly different from common types of aurora and occasionally indicated magnetic field–aligned substructures.
Observations from the Swarm satellite as it crossed the arc have revealed an unusual level of electron temperature enhancement and density depletion, along with a strong westward ion flow, indicating that a pronounced subauroral ion drift (SAID) is associated with this structure
New science in plain sight: Citizen scientists lead to the discovery of optical structure in the upper atmosphere
STEVE SAID ...
Scientists have now learned, despite its ordinary name, that Steve may be an extraordinary puzzle piece in painting a better picture of how Earth's magnetic fields function and interact with charged particles in space ...
Perhaps the biggest surprise about Steve appeared in the satellite data. The data showed that Steve comprises a fast moving stream of extremely hot particles called a sub auroral ion drift, or SAID. Scientists have studied SAIDs since the 1970s but never knew there was an accompanying visual effect. The Swarm satellite recorded information on the charged particles' speeds and temperatures, but does not have an imager aboard. People have studied a lot of SAIDs, but we never knew it had a visible light.
Steve consistently appears in the presence of auroras, which usually occur at a higher latitude area called the auroral zone. That means there is something happening in near-Earth space that leads to both an aurora and Steve. Steve might be the only visual clue that exists to show a chemical or physical connection between the higher latitude auroral zone and lower latitude sub auroral zone, said MacDonald.
Mystery of Purple Lights in Sky Solved With Help From Citizen Scientists | NASA
- STEVEs appears closer to the equator than where normal — often green — auroras appear. It appears approximately 5-10 degrees farther south in the Northern Hemisphere. This means it could appear overhead at latitudes similar to Calgary, Canada
- The phenomenon has been reported from the United Kingdom, Canada, Alaska, northern U.S. states and New Zealand
- STEVE is a very narrow arc, aligned east-west, and extends for hundreds or thousands of miles
- STEVEs mostly emits light in purple hues
- Sometimes the phenomenon is accompanied by a rapidly evolving green picket fence structure that is short-lived
- STEVEs can last 20 minutes to an hour
- STEVE has only been spotted so far in the presence of an aurora (but auroras often occur without STEVEs)
STEVEs may only appear in certain seasons. It was not observed from October 2016 to February 2017. It also wasn't seen from October 2017 to February 2018