How does the aurora borealis (the Northern Lights) work?

The northern lights, also known as the aurora borealis, have been a source of wonder for centuries. These mesmerizing light displays, dancing across the night sky, have inspired countless legends, myths, and tales. But what causes these ethereal lights? Let's dive in and unravel the mystery behind one of nature's most breathtaking phenomena.

The Science Behind the Northern Lights

Three key factors influence the stunning light show we see from Earth's surface: solar wind, Earth's magnetic field and atomic-level collisions.

Solar Wind

At the heart of the northern lights is the solar wind. This stream of charged particles, primarily electrons and protons, hurtles away from the sun at speeds of about 1 million miles per hour. Think of it as a cosmic painter, using the Earth's atmosphere as its canvas.

Earth's Magnetic Field

When these charged particles from the solar wind reach our planet, they're drawn towards the Earth's magnetic poles, thanks to the earth's magnetic field. This field acts like a protective shield, guiding these particles through the magnetosphere, a region teeming with electric and magnetic forces.

Collisions

As these electrons journey into the earth's upper atmosphere, they collide with atoms of oxygen and nitrogen. This is where the magic happens — depending on which atom they hit and at what altitude, different colors emerge:

Green: oxygen, up to 150 miles in altitude
Red: oxygen, above 150 miles in altitude
Blue: nitrogen, up to 60 miles in altitude
Purple/violet: nitrogen, above 60 miles in altitude

The Dance of the Auroras

The auroras are not static. They "dance" and shimmer, a result of the magnetic and electrical forces interacting in ever-changing combinations.

Imagine a ballet, but instead of dancers, you have atmospheric currents flowing with a staggering 20,000,000 amperes at 50,000 volts. For context, your home's circuit breakers would trip if the current flow exceeded just 15-30 amperes at 120 volts!

These light displays predominantly occur along the auroral ovals, which center on the magnetic poles. These aren't the same as the geographic poles we often think of, like the north pole. They align more closely with the Arctic and Antarctic circles. However, during periods of high sunspot activity, which follows an 11-year cycle known as the solar cycle, you can see the northern lights farther south.

Types of Auroras

The northern lights aren't the only auroras visible from Earth.

Solar Flares & Coronal Mass Ejections: These are particularly strong solar storms that can enhance the brightness and reach of the northern lights.
Aurora Australis: While the northern hemisphere has its light show, the southern hemisphere isn't left out. The southern lights, or aurora australis, dazzle the night sky in places like Australia and New Zealand.
Sun's Activity: The sun goes through cycles of activity, known as the solar cycle. Periods of high activity, or solar maximum, can lead to more frequent and vibrant auroras.

If you're trying to capture the beauty of the auroras, ensure you tweak your camera settings. A longer exposure can help capture their full majesty.

How the Northern Lights Illuminate the Night Sky