How Does the Aurora Work?

🌍 What Are the Northern Lights?

The northern lights — aurora borealis — are a natural light display in Earth's upper atmosphere. They appear as shimmering curtains, arcs or spirals of green, purple, pink and white light, usually visible between 65° and 72° latitude. Iceland sits almost perfectly inside this belt.

The aurora is caused by charged particles from the Sun colliding with gases in our atmosphere. When these particles hit oxygen and nitrogen, they release energy as light — creating the glow you see in the sky.

☀️ Why Do They Form?

The Sun constantly emits a stream of charged particles called the solar wind. During events like solar flares and coronal mass ejections (CMEs), it fires enormous bursts of plasma toward Earth at millions of kilometres per hour.

Earth's magnetic field normally deflects most of this, but at the poles the field lines converge — funnelling particles down into the atmosphere. That's why Iceland is one of the best places on Earth to see the aurora.

👁️ What Do You Need to See the Aurora?

Three things need to line up for a good display:

• Geomagnetic activity: Kp ≥ 2–3, negative Bz, high solar wind speed
• Clear skies: Cloud cover below 30% is ideal — clouds block everything
• Darkness: You need dark skies. In Iceland this means September–March, after astronomical twilight ends (usually 22:00–01:00 in winter)

Moon phase also matters — a full moon lights up the sky and reduces contrast. A new moon gives the darkest skies and the best aurora experience.

📖 How to Read the Kp Index

The Kp index is the most commonly quoted aurora metric. Here's a guide for Iceland:

❓ Why Does the Aurora Move and Dance?

The dancing motion is caused by rapidly changing magnetic field lines in the ionosphere. As the solar wind pressure fluctuates, charged particles follow different paths, creating the swirling, curtain-like motion that makes the aurora so mesmerising.

The most dramatic displays — known as auroral substorms — can fill the whole sky with rapidly shifting light within seconds. These happen when stored magnetic energy in Earth's magnetosphere is suddenly released.