Auroral Substorm over Iceland
Taken by Jeff Dai on October 6, 2026 @
Iceland
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Date Taken: 2026:10:08 01:34:07
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Why would an aurora suddenly burst into rare shades of pink and purple? Captured in a sequence of all-sky fisheye lens photographs taken at 30-second intervals, this series records the full progression of an auroral substorm unfolding high in the polar skies.
Auroras are generated by the interaction between charged particles from the solar wind and Earth's magnetosphere. When magnetic field lines in the magnetotail undergo explosive "magnetic reconnection," vast quantities of accelerated high-energy electrons cascade along the field lines into the upper atmosphere of the polar regions. In the first frame of the sequence, the night sky features only a faint and tranquil green arc. However, as the energy is instantaneously released, the aurora experiences a dramatic outburst within a matter of minutes.
The color of an aurora depends on both the energy of the incoming particles and the specific atmospheric gases being impacted. Typically, electrons collide with oxygen atoms at altitudes between 100 and 250 kilometers, exciting them to emit the familiar green glow at a wavelength of 557.7 nanometers. Yet, during the peak of the outburst (frames two through five), the electrons gain sufficient kinetic energy to penetrate much deeper, reaching lower altitudes below 100 kilometers. Here, they strike dense molecular nitrogen (N
2
), exciting it to produce vivid pink and purple hues—a blend of emission in red and blue wavelengths.
This vibrant pinkish-purple fringe clings tightly to the lower boundary of the auroral curtain, creating a striking contrast with the vast green expanse above. As the flow of energetic electrons gradually dissipates, the low-altitude pink luminescence fades away, leaving behind a diffuse green curtain that blankets the entire night sky. Below, the quiet contours of the hills and the calm water surface offer a tranquil reference point for this dynamic celestial spectacle.
photo taken on October 6th at Kirkjufell, Iceland.
Photographer's website:
https://www.instagram.com/jeffdaiphoto/
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