How far away can you see the aurora?
Despite popular belief you certainly don’t need to stand under the aurora to be able to see it. Most people don’t even realize they can actually see the lights from where they live if they know where and when to look…
People living in the polar cap will need to look south to spot the high latitude auroras (and everywhere else for daytime auroras). People living at high latitudes can have the aurora in the North, South or overhead depending on the strength of the activity. People living at lower latitudes will have to look North most of the time (and south for southern hemisphere inhabitants). You will see the phenomenon from a different angle because of your distance thus perhaps dimmer and less vibrant (see section on colors). Remember that the aurora is hundreds of kilometers in the upper atmosphere so you can see it from far away. The distances given below are approximative and depending on the brightness of the show you might be able to spot the event even further away.
Figure showing the different possibilities when looking at the aurora from more or less far.
Being under the aurora
When you see the aurora overhead, you’re theoretically only 80-100km below the closest glow. Besides there isn’t much atmosphere between you and the aurora to be a major obstacle like at lower latitudes so you see the aurora in its full glory. It means that when the aurora brightens up during a substorm and expands into a ‘corona’. The light show can literally cover all your sky from north to south. Since you sit right under the display the lower bright pinks and greens are the color you see the most because they outshine the reds and purples above. However certain coronas during strong geomagnetic storms produce rays that converge to the center of your view and you are able to see all the ‘height’ of the aurora with the greens and the reds/purples on top:
Taken in Medfjordvær, Senja, Norway in 2018
Standing under the aurora is the ultimate experience. Even if you can see and see the aurora at lower latitudes, this is what most people are traveling North to experience! Or you can always wait for the next G8-G9 geomagnetic storm if you live within the sub-auroral zone…
At around 300km from the aurora
When you are about 300 km away from the aurora display in Earth-projected distance, you observe the same aurora but lower in the sky. You will view it around 45° elevation (90° being the zenith). You are still close enough to be able to see bright and vibrant colors with the naked eye. Your perspective won’t enable you to experience overhead craziness but you have a very good angle that can potentially turn into your advantage for photography. You will most probably be able to peak at the full height of the aurora with the gradient of colors from green, red, purple and even blue!
Taken in Alberta, Canada in 2018
At around 600km from the aurora
When you’re viewing the same display from ~600 km you start getting a totally different experience. That’s what people would see (color excluded, see aurora color section) at lower latitudes during a G1-G2 storm. This picture was taken in Denmark during a G2 peak.
At this distance you see the aurora on the horizon at 10-25° elevation (northern horizon for aurora borealis and southern horizon for aurora australis). You have a lot of atmosphere between you and the display plus you get this bending effect (loupe) so the aurora appears dimmer and less colorful. The bright greens are lower, sometimes so close to the horizon that its color is shifted. Much like the sun turns orange during a sunset! You can still be in for a tremendous show of dancing pillars on the horizon though and I can’t recommend enough chasing the lights at lower latitudes too! Taking pictures of the aurora then will give you better results than the naked eye.
At around 900km from the aurora
Taken in Denmark in 2016
The visibility line is not really a very defined science because it depends on so many intrinsic factors but we usually define it as the line where it becomes pointless for both naked eye and photography. You might be lucky and catch a shot or two of the red/purple end of high pillars but most of the aurora is below the horizon.
As a conclusion you can see the aurora from many places in the world. Most of them are unsuspected because they’re usually on the horizon and not so colorful. If you really want to see the spectacular colors you’d better book a trip to northern Norway for example!