The Northern Lights: A Spectacular Display Influenced by Climate Change

The night sky over Iceland’s iconic Kirkjufell volcano is illuminated by the aurora borealis. These stunning lights occur when charged particles from the sun collide with gases in Earth’s atmosphere, with the colors indicating the specific atmospheric layer where these interactions take place. Image  by  BABAK TAFRESHI 

By Rashmitha Diwyanjalee

What are the Northern Lights?

The Northern Lights, or aurora borealis, are a breathtaking natural light display commonly seen in the night sky of the northern hemisphere. They occur when charged particles from the sun collide with gases in Earth’s upper atmosphere, producing vibrant colors like green, pink, red, blue, and purple. These lights, known as polar lights or aurora polaris, also appear in the southern hemisphere as the southern lights or aurora australis.

The Northern Lights, or aurora borealis, can sometimes appear in unexpected places due to a combination of solar activity and Earth’s magnetic field dynamics. The related article can be reached here. 

How Do Auroras Form?

Earth’s magnetic field lines. Image credit: NASA’s Goddard Space Flight Center.

Auroras are the result of interactions between the solar wind—a stream of charged particles from the sun and Earth’s magnetic field. This field acts as a shield, deflecting most solar particles. However, near the poles, where the field lines converge, some particles penetrate the atmosphere, leading to collisions with oxygen and nitrogen molecules. These collisions excite the gas molecules, causing them to emit light as they return to their ground state. 

(The original video can be watched in Canadian Space Agency`s web from here )

The Chemistry behind the Aurora Borealis, or Northern Lights

Earth’s magnetosphere shields us from most solar particles, but some manage to penetrate through a ‘cusp’ in this shield, creating the daytime aurora. Most solar particles enter the magnetosphere on the night side and travel along magnetic field lines towards the polar regions (T. Abrahamsen/ARS)

The stunning displays of the aurora borealis, or Northern Lights, are a result of complex interactions between charged particles from the sun and gases in Earth’s atmosphere.

Solar Wind and Charged Particles: The sun constantly emits a stream of charged particles known as the solar wind. These particles are primarily electrons and protons. During periods of intense solar activity, such as solar flares and Solar Flares and Coronal Mass Ejections (CMEs), the number of charged particles released increases significantly.

Collision with Atmospheric Gases: When these high-energy charged particles collide with gases in Earth’s upper atmosphere (the thermosphere and exosphere); they transfer energy to the gas molecules. This energy transfer excites the electrons in the gas molecules, causing them to jump to higher energy states.

Emission of Light: As the excited electrons return to their original energy levels, they release the absorbed energy in the form of light. This process is called photon emission. 

Solar particles collide with atmospheric atoms, causing their electrons to move to higher orbits. When these electrons return to their original orbits, they release energy as light (T. Abrahamsen/ARS).

Altitude Variations: At higher Altitudes (above 150 km), oxygen atoms are more prevalent and typically produce red and green colors. At Lower Altitudes (below 150 km), nitrogen molecules dominate and produce blue and purplish-red colors. Read more on Canadian Space Agency.

Therefore, the auroras’ colors depend on the type of gas and the altitude at which the collisions occur:

• Green: The most common color, produced by oxygen molecules at altitudes of 100 to 300 km.
• Pink and Dark Red: Produced by nitrogen molecules at around 100 km altitude.
• Red: Produced by oxygen atoms at altitudes of 300 to 400 km.
• Blue and Purple: Produced by hydrogen and helium molecules, although these colors are harder to see against the night sky.

The ionosphere, a layer of charged particles in Earth’s atmosphere, extends from about 50 to 360 miles above the surface. Processes within this layer also create bright swaths of color in the sky, known as airglow. Image by : NASA

Impact of Climate Change on the Northern Lights

While the Northern Lights are primarily driven by solar activity and Earth’s magnetic field, climate change can influence this natural phenomenon in several indirect ways:

1. Changes in Earth’s Magnetic Field: Climate change can alter the geomagnetic field, potentially affecting the patterns and intensity of auroras. The magnetic field is generated by the convective flow of molten metal in Earth’s outer core. Changes in the core’s motion, influenced by climate variations, and could impact the magnetic field’s behavior. The related articles can be reached here and here.
2. Atmospheric Changes: Climate change leads to shifts in atmospheric conditions, including humidity, temperature, and air composition. These changes can affect aurora visibility. For instance, increased cloud cover or altered atmospheric layers might obstruct the view of auroras. The related articles can be reached here and here.
3. Solar Activity and Geomagnetic Storms: Although solar activity itself is not influenced by climate change, our ability to monitor and predict solar events could be impacted. Intense geomagnetic storms, associated with heightened solar activity, enhance auroras displays. Climate-related changes in the magnetosphere and ionosphere could indirectly influence these storms. The related articles can be reached here and here.
4. Viewing Opportunities: As the climate warms, shifts in weather patterns may alter the best times and locations for observing the auroras. Regions traditionally known for aurora viewing might experience changes in visibility due to varying climatic conditions.

The Complexity of the Relationship

The link between climate change and the Northern Lights is complex and not fully understood. The primary drivers—solar activity and Earth’s magnetic field—are influenced by factors beyond climate change. However, climate change can indirectly affect the Northern Lights by altering atmospheric and geomagnetic conditions. Ongoing research aims to unravel these interactions and predict how future climate changes might impact this mesmerizing phenomenon. 

On December 25 and 26, 2022, researchers documented a rare polar rain aurora from Longyearbyen, Norway, visible beneath the more common aurora borealis. Polar rain auroras form through a different mechanism than typical auroras and are extremely difficult to observe. Image by: FREDRIK MELING

Therefore, the Northern Lights are a natural testament to the dynamic interactions between the sun and Earth. Climate change has the potential to influence their visibility and intensity through indirect effects on the magnetic field and atmospheric conditions. As we continue to study these relationships, we gain a deeper understanding of how our changing planet impacts the natural wonders that have fascinated humanity for centuries.