Light show in the sky - How are the northern lights created?
Auroras occur in regions known as auroral zones. These zones form ring-shaped belts around the Earth, near the magnetic poles. They are located about a few thousand kilometers from the North and South Poles. It is estimated that auroras occur in these zones about 200 nights per year.
How Auroras Are Created
The Northern Lights are a natural phenomenon caused by the interaction between the Sun and our planet.
The process begins when electrically charged particles from the Sun—known as the solar wind—enter the Earth's atmosphere and encounter atoms and molecules in the upper atmosphere.
Although Earth's magnetic field protects us from most of the solar wind, some particles manage to reach the Earth’s magnetosphere, where they are guided into the atmosphere by the magnetic field. Particles arriving from space give the atoms and molecules in our atmosphere additional energy, which they release by emitting colored light. This coloured light is what we see as the Aurora Borealis (Northern Lights) or Aurora Australis (Southern Lights).
Each aurora display is unique. The lights in the sky can appear and fade multiple times during a single night — even up to 3 to 5 times. Displays may last for just a few minutes or, in some cases, continue for several hours or more.
Aurora Colors and Altitudes
The four main colors of the aurora colors are considered to be green, red, violet, and blue.
The color of the aurora is influenced by the excited particle and the energy it receives in the collision. The most common and the strongest color is yellow-green, that comes from oxygen atoms. In the northern hemisphere, auroras typically appear green, with a wide variety of shapes. When the aurora is especially strong, other colors may also be visible.
Red auroras are also caused by oxygen atoms. In the south, the color of the auroras is usually red. In the south, the auroral shapes tend to be more scattered compared to the north.
Blue and violet hues are emitted by nitrogen. In addition to the main colors, auroras may sometimes appear to have other colors, such as white, yellow, gray, or pink.
Auroras can occur at altitudes between 65 and 1,000 kilometers. Different colors are produced at different heights:
• Blue light tends to appear around 100 km
• Green light between 100–170 km
• Red light from above the green light up to about 300 km
The many names of the Northern Lights
In almost every language, the word for auroras refers to either the northern or southern lights. In English, they are called Northern Lights (Aurora Borealis) in the northern hemisphere, and Southern Lights (Aurora Australis) in the southern hemisphere. Collectively, they are often simply called auroras.
In Finnish, the word revontuli originates from ancient beliefs about the phenomenon’s origin. Other Finnish names for auroras include rutjat, taivaanvalkeat, and pohjanpalot — all rooted in folklore and oral tradition.
Did you know? ☀️
• Aurora was the Roman goddess of the sunrise. Her name began to be associated with the Northern Lights in the early 17th century.
• Earth is not the only place where auroras occur. They have also been observed on Saturn, Jupiter, and Uranus.
Recommended Reading (mostly in Finnish) 📚
Below are some recommended books for those interested in learning more about the Northern Lights. These have also served as background sources for the content on this website:
• Palmroth, Minna; Jussila, Jouni; Hotakainen, Markus. Revontulibongarin opas. Into Kustannus Oy, 2018.
A collaborative guide by space experts and aurora enthusiasts. Includes stunning aurora photos and practical tips for aurora hunting and photography.
• Evans, Polly. Northern Lights – A Practical Travel Guide. 4th ed. Brad Guides Ltd, 2023 (1st ed. 2010).
A travel guide with both information on auroras and useful travel tips.
• Jussila, Jouni. Aurora – Revontulien taivaallinen näytelmä. WSOY, 2002.
Researcher Jouni Jussila explains how auroras are formed and how to photograph them. Includes his own aurora photography.
• Kaila, Kari. Revontulet – Kansankäsityksistä tutkimukseen. Gummerus Kirjapaino Oy, 1998.
A broad look at the history of the Northern Lights and traditional beliefs, written by researcher and docent Kari Kaila.
• Luhta, Jorma; Paasonen, Seija. Revontulet. Maahenki Oy, 2019 (2nd ed.).
Features aurora photos by nature photographer Jorma Luhta and informative sidebars by meteorologist Seija Paasonen on auroras and related folklore.
• Nevanlinna, Heikki. Revontulet – Tarua ja totta. Ilmatieteen laitos – geofysiikan tutkimus, 1997 (2nd ed.).
Information about the auroras, for example the best times and places to view them.
• Pirttimaa, Markku; Valtaoja, Esko. Revontulten tanssi. The Dancing Northern Lights. Mäntykustannus Oy, 2011.
A combination of aurora photography by Markku Pirttimaa and informative astronomy texts by Esko Valtaoja.
• Turunen, Pertti (photos); Linnilä, Kai; Savikko, Sari (text). Lapin Valot. Oy Amanita Ltd, 2011.
A photo book and reference guide featuring the landscapes and light phenomena of Lapland, including the Northern Lights.
In addition to literary sources, this content was informed by the exhibition Vastakohtien Arktis ("in english: Contrasts of the Arctic") at the Arktikum Museum in Rovaniemi. The exhibition opened in December 2024.