Last night we were treated to the spectacle of the Northern Lights here in the North West of England. My Facebook feed was flooded with images of the amazing Aurora Borealis as my friends headed to the hills and looked to the skies hoping to catch a glimpse of the cosmic display.
What are the Northern Lights?
The Northern Lights or Aurora Borealis are a spectacular light show. Colours in the sky appear as bright swirling colours. They can be bright pinks, reds, greens, blues or even purples. They typically appear in regions close to the North Pole. The Aurora Australis is the light show that appears in regions close to the South Pole. The highest point of the aurora can be as high as 150 miles above the earth’s surface and the lowest around 50 miles from the surface.
What do the Colours mean?
Here’s a table summarizing the different colors of the northern lights and what they signify, based on the altitude at which they occur and the gases involved in creating them:
| Color | Gas Involved | Altitude | Cause/Meaning |
|---|---|---|---|
Green | Oxygen | 100 – 300 km (62 – 186 miles) | A rarer colour, caused by high-altitude oxygen. Typically seen during intense solar activity. |
Red | Oxygen | Above 300 km (186 miles) | A blend of red and blue/purple light from nitrogen and oxygen, is often seen when the aurora is very active. |
Purple/Violet | Nitrogen | Below 100 km (62 miles) | Produced when charged particles collide with nitrogen at lower altitudes, leading to purple or violet hues. |
Blue | Nitrogen | Below 100 km (62 miles) | A less common colour, also caused by nitrogen, occurs at lower altitudes where collisions are more intense. |
Pink | Nitrogen + Oxygen | Variable, usually lower altitudes | A blend of red and blue/purple light from nitrogen and oxygen, often seen when the aurora is very active. |
This table helps explain how the varying gases and altitudes in the atmosphere contribute to the distinct colours in the northern lights display.
What Causes the Northern Lights?
The Solar Wind and the Sun’s Role
The northern lights begin with the sun, a vast sphere of hot plasma that constantly emits energy and particles into space. This flow of charged particles, primarily electrons and protons, is known as the solar wind. While the sun continually releases a steady stream of solar wind, it also undergoes periods of heightened activity, such as solar flares and coronal mass ejections. These events dramatically increase the number of charged particles travelling through space.
As the solar wind travels toward Earth, it encounters the planet’s magnetic field. The Earth’s magnetic field serves as a protective shield, deflecting most of these charged particles away from the planet. However, some of these particles manage to penetrate this shield, particularly near the polar regions, where the magnetic field is weaker and forms funnel-like structures that guide these particles toward the Earth’s atmosphere.
The Role of Earth’s Magnetic Field
Earth’s magnetic field plays a crucial role in the formation of the northern lights. This magnetic shield extends into space and forms what is known as the magnetosphere, which surrounds the planet like a protective bubble. While the magnetosphere deflects most of the solar wind, it’s the interaction between the magnetic field and the charged solar particles that creates the auroras.
When the charged particles from the solar wind collide with the magnetosphere, they are guided along Earth’s magnetic field lines toward the poles. These lines converge at the magnetic poles, which is why auroras are typically seen in high-latitude regions near the Arctic and Antarctic circles.
Interaction with the Atmosphere: The Light Show
As the charged particles follow the magnetic field lines and enter the Earth’s atmosphere, they collide with gas molecules, particularly oxygen and nitrogen. These collisions transfer energy to the atmospheric gases, exciting the atoms and causing them to emit light as they return to their normal state. This process is similar to how neon signs work—electrons are excited and release photons (light) as they stabilize.
The specific colours seen in the aurora depend on the type of gas involved and the altitude at which the collisions occur. Oxygen, for instance, emits green or red light, depending on the altitude of the collision. Green is the most common auroral colour and typically occurs at altitudes between 100 to 300 kilometres. Red auroras, which are rarer and occur at higher altitudes, resulting from oxygen particles interacting above 300 kilometres.
Nitrogen, on the other hand, produces purples and blues. At lower altitudes, nitrogen molecules emit a purplish-pink hue when they collide with charged particles. The variation in colours and patterns of the northern lights creates an ever-changing visual spectacle that can last for several minutes or even hours.
The Influence of Solar Storms
While the solar wind is constantly bombarding Earth, the intensity of the northern lights fluctuates based on solar activity. During periods of heightened solar activity, such as during solar flares or coronal mass ejections, the amount of charged particles increases dramatically. These solar storms can amplify the strength and visibility of auroras, pushing them further south than usual. This is why, during periods of high solar activity, people living in regions outside the polar latitudes, such as northern Europe or the northern United States, may also witness the aurora borealis.
Why Can We See the Northern Lights in the North West?
2024 is the most active the sun will be in its 11-year solar cycle. This means there are more solar storms and the sun’s magnetic field is becoming stronger thus making seeing the Northern Lights in North West England more and more likely.
What are the best conditions?
You will have the best chance of seeing the Northern Lights on a clear, cloudless night. Try your best to get away from light pollution and head for the hills. The higher you are, the more likely you will be able to see them due to lack of obstruction. Having said that, I have driven to the desolate Saddleworth moors to view the lights but could also see them in my back garden in the middle of the town.
You’ll likely only see the Northern Lights through your phone. If you take time for your eyes to adjust to the darkness, it is possible to see the lights with the naked eye. From the moors, it was possible to see the lights moving with the naked eye. Each time I have seen them, it has been a phenomenal experience.
Here are some of our images from our back garden.
For similar posts, see my Home Life Category.
