Aug 17, 2019 | Updated: 07:24 AM EDT

Goodbye, Aurora; Hello, STEVE

May 13, 2019 07:19 AM EDT

Steve is an atmospheric optical phenomenon, which appears as a light ribbon across the sky.
(Photo : Elfiehall)
STEVE is an atmospheric optical phenomenon, which appears as a light ribbon across the sky.

The aurora borealis is one of the most spectacular phenomena that skywatchers are always keen on catching. It has colored the night sky over the past decade when the conditions in the atmosphere permit it. Skywatchers were always counting on forecasts for sightings of the majestic phenomenon.

However, according to scientists, the current condition of the atmosphere is showing signs of the decreased occurrence of the northern and southern lights. In place, a new phenomenon that is similar to the aurora borealis which also involves a spectacular display of lights is starting to frequent the night sky. They call this new phenomenon STEVE or Strong Thermal Emission Velocity Enhancement.

Apart from their different colors, the aurora borealis being green and the STEVE being mauve and purple, there are other differences that set the light displays apart.

While the aurora borealis is being caused by charged particles heating atoms and molecules in the atmosphere of the Earth, the STEVE is caused by ions that flow east to west at nearly 6 kilometers per second as propelled by electric and magnetic fields in the atmosphere. 

The aurora borealis is often green because it is the color that oxygen atoms emit in the atmosphere of the Earth. Whereas, the motion of the ions contribute to the STEVE's purple hue, 

When it comes to appearance, the aurora borealis appears in a diffused glow of lights the northern or southern horizon. On the other hand, the STEVE occurs in a band of light that stretches east to west and fuse in much lower latitudes. It sometimes has a second arc known as a "picket fence", which appears in green color.

Chris Ratzlaff, the head of a citizen-scientists group from Alberta, Canada gave the name STEVE to the light display after a line from the movie "Over The Hedge," which debuted in 2006.

Elizabeth MacDonald and her team used the data from Swarm-A, a European satellite, to study the new phenomenon. The scientists stated that they have observed that STEVE appears about 200 km up in the atmosphere. They also have confirmed that the charged particles reach a temperature of 6000°C. The scientists explained that the east to west movement of the ions is influenced by the electric and magnetic fields in the Earth's atmosphere. Although the heat and motion are identified to contribute to the purple hue, which mainly causes the blend of the said colors is yet to be identified.

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