New analysis confirms hypothesis for source of mysterious auroral “dunes”

Revisiting the aurora "dunes": A time-lapse video recorded by a Scottish aurora borealis hobbyist Graeme Whipps was used to determine the speed of the phenomenon at over 200 m/s.

Several years ago, amateur astronomers first spotted a rare type of aurora nicknamed "the dunes" because of its luminous, rolling wave patterns. Last year, astronomers proposed a possible underlying mechanism-an increase in the density of oxygen atoms-although the theory was admittedly speculative. Now, a new analysis by researchers at the University of Helsinki provides evidence to confirm that explanation, according to a recent paper published in the journal AGU Advances.

Most people have a passing familiarity with the atmospheric phenomenon known as the northern lights (or the southern lights if they appear in the southern hemisphere). The spectacular kaleidoscopic effects are the result of charged particles from the Sun being dumped into the Earth's magnetosphere, where they collide with oxygen and nitrogen molecules-an interaction that excites those molecules and makes them glow. Auroras typically present as shimmering ribbons in the sky, with green, purple, blue, and yellow hues. The lights tend to only be visible in polar regions because the particles follow the Earth's magnetic field lines, which fan out from the vicinity of the poles.

Discoveries of possible new types of auroras are rare. Back in 2016, enthusiasts observed a different kind of aurora that was visible at more southern latitudes. The aurora looked like a ribbon of pink or mauve light, sometimes with "picket fence" columns of green light passing through the ribbon.

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