Northern Lights Illuminated: The Science Behind the Aurora

 by Harvey Xu

Imagine you're standing under a starlit sky far away from the city's dazzling lights. Above, the sky illuminates into a symphony of colours which paints the night with hues of pink, purple and green. The Northern Lights (also known as Aurora Borealis) showcases a mesmerising picture in the sky and a spectacle that has amazed observers throughout history. This natural display characterised by vibrant colours swirling in the night sky is not just a visual marvel but also a fascinating scientific phenomenon.

The story begins 93 million miles away on the surface of the Sun. The Sun is constantly emitting streams of charged particles known as the solar wind. This wind travels across the solar system carrying pieces of the Sun's magnetic field which eventually reaches Earth. Our planet is shielded by its own magnetic field which is created by the motion of molten iron in its core. When the solar wind reaches Earth, charged particles from the Sun are funnelled towards the poles by Earth's magnetic field. As these charged particles enter Earth's  atmosphere they collide with gas molecules such as oxygen and nitrogen.

Each collision releases a tiny burst of light. It's like a neon sign, where electricity energises gas particles to glow. Multiply these tiny flashes by countless trillions, and you get the fantastic spectacle of the Northern Lights. The colour of the aurora depends on which gas is involved and how high in the atmosphere the collision occurs. Oxygen (about 60 miles up) gives off a green colour which is the most common hue of the aurora. Higher up, however, can create a rare all red aurora. Nitrogen produces blue or purplish-red aurora. 

The intensity of the Northern Lights can also be linked to the activity on the Sun as during solar maximum, which is a period of high solar activity in the Sun's 11-year cycle, the auroras are more frequent and vivid. But they are not just limited to the poles. When there is a strong solar storm, they can be seen at lower latitudes offering a rare sight to those far from the polar regions. 

Watching the Northern Lights isn't just a tick on a traveller's bucket list, it's a glimpse into the complex science around us. This phenomenon is not just a visual presentation but also a demonstration of the dynamic nature of space weather. As observers stand under the auroral display, they are witnessing a small part of the vast and intricate workings of our solar system.