What's STEVE? After auroras, purple & green lights in skies dazzle earthlings

We humans often think we know what nature is and put it into scientific calculations and poetic stanzas. But nature always surprises us with its intractability and that’s the beauty of it. Such is the case with green and purple lights spotted in the northern skies which everyone assumed to be auroras, the bright colours that adorn the skies when solar storms hit the Earth's atmosphere. But what if we tell you that these green and purple lights were a completely different phenomenon? 

The purple and green ribbons of light in the sky hovering over the horizon in the Northern Hemisphere are not auroras, but STEVE or Strong Thermal Emission Velocity Enhancement.

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This rare atmospheric phenomenon has caused a lot of buzz this year, as more and more people spotted Steve in areas it does not usually appear, such as parts of the United Kingdom. 

STEVE is an atmospheric optical phenomenon that appears as a purple and green light ribbon in the sky. It was named in recent years in 2016 by aurora watchers and enthusiasts from Alberta, Canada. 

Though it caught the attention of auroral photographers recently, some evidence suggests that STEVE observations may have been recorded as early as 1705. But at that time, no one knew what exactly it was.

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The first accurate determination of the nature of the phenomenon was not made until after members of a Facebook group, Alberta Aurora Chasers, named it, attributed it to a proton aurora, and began calling it a "proton arc".

As of March 2018, the STEVE phenomenon has been observed in the United Kingdom, Canada, Alaska, the northern US States, Australia and New Zealand. It appears as a very narrow arc extending for hundreds or thousands of miles, aligned east-west. It generally lasts for 20 minutes to an hour. In March 2018, STEVE phenomena was spotted in the presence of an aurora. 

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A meeting of aurora enthusiasts in a small Canadian pub was the turning point in their quest to understand STEVE. It was here, where the phenomenon was named Strong Thermal Emission Velocity Enhancement or STEVE.

While STEVE is only spotted in the presence of an aurora, it is not a normal aurora as scientists suggest it comprises a fast-moving stream of extremely hot particles called a sub-auroral ion drift or SAID.

Earth is entering a period of enhanced solar activity, or solar maximum, which occurs every 11 years. During this time, spectators can expect more visible light shows in the sky and a chance to witness a STEVE at low latitudes.

STEVE is best seen through the lens of a camera. However, to the naked eye, it can appear as nothing more than what looks like a faint contrail from an aeroplane streaking across the sky and hence can be easily overlooked. They are typically seen between evening and midnight.