Blue, purple and green auroras electrify northern sky

Blue, purple and green!

The G2 geomagnetic storm on September 16, 2017, was so powerful that even blue and purple colors appeared ontop of green.

Blue purple and green aurora on September 16 2017, northern lights september 2017, amazing northern lights september 2017
Blue purple and green aurora on September 16 2017. via Alexander Golubev

The majority of auroral displays are predominantly green because the human eye detects green more readily than other colours.

Blue purple and green aurora on September 16 2017, northern lights september 2017, amazing northern lights september 2017
Blue and purple northern lights normally form when the solar activity is high. via Alexander Golubev

The main factor in determining the colours of any given northern lights is altitude, because different gases prevail (or are spayed) at different altitudes and in varying concentrations. It is the collision which “excites” these gases that determines the colour of the Aurora.

Blue purple and green aurora on September 16 2017, northern lights september 2017, amazing northern lights september 2017
A watch has been issued a G2 (Moderate) geomagnetic storm conditions on 16-17 September 2017 by NOAA. via Alexander Golubev

We don’t see red in the Aurora Borealis too frequently and the colour tends to be associated with intense solar activity. Reds appear when solar particles react with Oxygen at higher altitudes, generally above 150 miles.

Blue purple and green aurora on September 16 2017, northern lights september 2017, amazing northern lights september 2017
Purple and blue auroras normally appear towards the lower parts of the northern lights display. via Alexander Golubev

When red mixes with green or blue, you can see yellow and pink in an northern lights display associated with high solar activity.

Blue purple and green aurora on September 16 2017, northern lights september 2017, amazing northern lights september 2017
So was the auroral display more violent than expected in September 2017? via Alexander Golubev

Most solar particles typically collide with our atmosphere at an altitude of around 60 to 150 miles where there are high concentrations of oxygen. When the Oxygen is “excited” at these altitudes it causes the Aurora to appear in shades of green.

Blue purple and green aurora on September 16 2017, northern lights september 2017, amazing northern lights september 2017
Another sky anomaly. via Alexander Golubev

Finally, blue and purple are also colours which are seen less frequently, because they only tend to appear when solar activity is high. Purple or blue auroras are produced by nitrogen colliding with our atmosphere at altitudes of 60 miles or less.

Blue purple and green aurora on September 16 2017, northern lights september 2017, amazing northern lights september 2017
Are we being chemtrailed? via Alexander Golubev

Most commonly, blue and purple appear in the lower parts of the display, which is not the case in these pictures.

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