Urban experiences meet raw Arctic nature
Tromsø
Kari Schibevaag
What causes the northern lights?
The northern lights are created when energetic particles interact with Earth’s magnetic field and enter the upper atmosphere. There, they transfer energy to oxygen and nitrogen atoms and molecules. When these gases release the energy, they emit light in different colours, creating the aurora we see in the night sky.
How does the Sun create the northern lights?
The Sun continuously releases a stream of electrically charged particles known as the solar wind. Changes in the solar wind, and large eruptions called coronal mass ejections, can transfer energy to Earth’s magnetic field. A coronal mass ejection, or CME, is a cloud of plasma and magnetic field released from the Sun. It is different from a solar flare, although the two phenomena can occur together.
What happens when the particles reach Earth?
Earth’s magnetic field shields the planet from most of the solar wind. However, interactions between the solar wind and the magnetic field can release energy and accelerate particles towards the polar regions. When these particles enter the upper atmosphere, they collide with oxygen and nitrogen. The gases then release energy as visible light.
Why do the colours vary?
The colour of the aurora depends on the gas involved and the altitude at which the interaction occurs. Green, the most common colour, is mainly produced by oxygen. Oxygen at higher altitudes can create red aurora, while nitrogen contributes blue, purple and pink colours.
How high are the northern lights?
Most visible aurora occurs roughly 80–300 kilometres above Earth, although some forms can appear at higher altitudes. This is far above clouds and other weather systems. Cloud cover does not affect the aurora itself, but it can prevent people on the ground from seeing it.
Why can we see the northern lights in Tromsø?
Tromsø is located within the auroral zone, an area surrounding the geomagnetic pole where northern lights frequently occur. The exact position and size of the auroral oval vary with geomagnetic activity, but Tromsø’s location gives visitors the possibility of seeing aurora even when activity is relatively low.