When aurora is low, it appears as a white widespread brightness in the empty sky.
Why white?
Because of when solar wind is not so powerful, the energy of photons emitted by oxygen (molecular and atomic) and by nitrogen, are so low that we watch light using only rod cells of our retina, and rod cells permits us to watch only in black and white. Conversely, sensors of a reflex/mirrorless/smartphone camera, can watch full colors! So when we see a white brightness, it has colors... It is very strange, but it is a fact, and I reflect about what is reality and what is not reality. Our senses are limited, so we can't trust in our sense to understand reality. Also low intensity auroras is colorful, but we can't watch colors!
Here an example: this is a long exposure (30 seconds) pictures where auroras appeared as white:
But wow! There are many colors!
When auroras increases its intensity (more density in solar wind), colors suddenly appears! Like in the following pictures.
In the first, you can see also last twilight colors on the horizon:
And the last one, one of my favorite!
That auroras was fully visible by our retina, not only with rod cells, but with the greater contribute of cones cells inside retina, so colors appeared (cones cells are responsible of colors) not only with sensors, but also with naked eye!
In last image I have joined two different shots (some seconds between first and second shot), to recreate the reflection of the green on ocean surface, because of a wide angle (24mm) was not enough!
Thanks to my friend, director and physicist Luca Giberti for technical advices and suggestions!
Pictures taken with a Sony Alpha 7iii camera.
Vestersand, Vestvågøy island, Lofoten, Norway. On background Eggum cape.
Nights between 27 and 28, and between 28 and 29 march 2024.
