Why is Steve such a special Northern Lights?

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Purple and green colors in the sky, out of the ordinary, caused scientists to turn to see a celestial spectacle that they now call Steve , an aurora borealis that appeared two years ago.

But what is special about this phenomenon? It turns out that this aurora borealis had not been documented in the scientific field. So much so that it is not known how it was formed , according to NASA . However, they also pointed out that Steve is not a normal aurora.

"The auroras are presented in oval form in the last hours of the day and are mainly seen in green, blue and red colors",
NASA

What makes the Northern Lights Steve unique?
This aurora is purple , with a structure of green fences that curves. It is a line with a beginning and an end, according to NASA.
The phenomenon lasts between 20 minutes and an hour.
The famous aurora appears at low latitudes or in the subauroral zone , which causes it to be seen as far as southern Canada.
Steve is also seen in the auroral zone , so there is a chemical or physical connection between both regions.
It has been seen from the United Kingdom, Canada, Alaska, northern states of the United States and New Zealand.
It only appears at certain times , it had not been observed from October 2016 until February 2017 and after October 2017 until February 2018.