The northern lights, or auroras, are one of the most amazing sights of our planet. They can be observed on the night skies of the northernmost and southernmost regions of Earth, but are hard to predict with accuracy.
This guide is divided into the following sections: what are the northern lights, how to predict them, where to see them and how to see them.
In this guide you will understand why they are so unpredictable, how to predict them as precisely as possible, and how to see them when they’re out there.
What are the northern lights?
Auroras are even more awesome when you understand how they are formed.
First, know that the Earth has a magnetic field that shields the planet from the incoming particles coming from the Sun (as a result of solar eruptions, these particles travel to Earth as “solar wind” and need about 3 days to reach the planet).
The diagram below quickly summarizes the main areas of the magnetosphere, with the incoming solar wind represented as well. Basically, charged particles follow the magnetic field lines, some of which are drawn in black.
Particles from the Sun are either pushed towards the plasma sheeth or fall directly into the polar cusps (aurora regions on the north and south poles); the particles in the plasma sheet will then either fall into the magnetotail and be gone forever, or return to Earth through the neutral point.
Both the particles that fall directly to Earth and the particles coming from the back of the magnetosphere go into the polar cusps, down to the poles, and collide with particles in the atmosphere. During these collisions, a portion of the particles’ energy is released in the form of light, thus creating the lights.
The wavelength of this released energy/light will determine the color of the display; green being the most typical one (it corresponds to the most stable transition of energy levels in the collision).
Where to see them
Although “northern lights” (aurora borealis) is the most popular name for the auroras, these polar lights also happen in the Antarctic region of the southern hemisphere, where they are called “southern lights” (aurora australis).
A rule of thumb is that lights can be spotted from places above the Arctic Polar Circle in the northern hemisphere and below the Antarctic Polar Circle in the southern hemisphere.
However, if the magnetic activity is strong enough, auroras can be spotted from places closer to the equator. Since there is little inhabited land that falls within the Antarctic Polar Circle, chasing the southern lights is a much more challenging adventure.
The northern lights can be easily spotted from cities and towns in the northernmost regions of many countries. Typical areas where people travel to see them include:
- Alaska: Denali National Park
- Canada: Yellowknife, Yukon, Northern Saskatchewan
- Finland: Inari, Kakslauttanen
- Greenland: Kangerlussuaq
- Iceland: anywhere
- Norway: Lofoten archipelago, Alta, Karajosk, Tromsø, Svalbard island
- Russia: Murmansk
- Sweden: Abisko, Kiruna, Jukkasjärvi
And, of course, the South Pole in Antarctica.
How to predict the northern lights
There are many aurora forecasts websites and apps.
Basically, what they measure is the magnetic activity. A stronger magnetic activity translates into more collisions happening, so the chances of auroras happening are higher.
This is represented as Kp index that goes from 0 to around 9. The higher the index, the stronger the magnetic activity, and the easier it is to spot the northern lights.
Additionally, a correlation is possible between the index and the minimum latitude needed to see the lights. For example, if you are in Abisko (Sweden), a kp index of 3 may be enough to see the lights; but you won’t see them from Stockholm.
If the index gets as high as 7, the lights will be brighter and easier to be seen in Abisko, and it will also be possible to see them from Stockholm.
This following diagram (or a similar one) is typically featured on any aurora forecast website or app. In this case, it shows a kp index of 3, which is low. Note that the colors of the diagram have nothing to do with the colors of the northern lights.
Nonetheless, if you are above the polar circle, the kp-index is not that precise: while an index higher than 5 is a pretty solid indicator, auroras can show up for very low indexes as well. Before winter-dressing up, make sure to check all-sky cameras.
These are cameras that constantly take pictures of the sky. If the auroras are out there, the nearest all-sky camera will show bright colorful lines.
Some all-sky cameras throughout the globe are:
- Canada: Yellowknife
- Finland: Sodankylä, others
- Norway: Tromso, Longyearbyen (Svalbard island)
- Sweden: Abisko, Kiruna
How to see them
Auroras cannot be observed in the summer because the sky is too bright. They are typically observable from mid-September till mid-April in the northern hemisphere. The ideal conditions to see the northern lights are:
- Dark sky (new moon nights being the perfect scenario).
- Strong magnetic activity (check aurora forecast); at least kp index = 3 for any of the cities mentioned above.
- Cloudless sky (look up or check weather forecast).
Although lights can be seen from the city, it does help a lot to get out and find a place in the woods where the light pollution is blocked by a hill or the forest.
Since it will be cold winter, make sure to bring warm boots, socks and gloves. You will very much feel the freeze while waiting for the first auroras to show up. Once they do, you will completely forget about the cold!
How to shoot them
Taking good pictures of the northern lights requires some knowledge of your camera.
There is extensive literature online on “how to photograph the northern lights”. My recommended setup is:
- Exposure time: 20 seconds.
- Lens: wide angle, 35mm.
- ISO: 2,500 or higher.
- Aperture: f/2.8 or faster.
If you are not that into photography, it is possible to capture the northern lights with a smartphone. The picture will be very bad, but makes up for a souvenir to take home with you. Something’s better than nothing.