What Causes the Northern Lights to Dance?

The Northern Lights are created when charged particles from the Sun interact with gases high in Earth's atmosphere.

The particles travel towards Earth in the solar wind. When they reach our planet, Earth's magnetic field guides many of them towards the polar regions.

High above the ground, the particles collide with gases such as oxygen and nitrogen. These collisions release energy as light, creating the aurora.

The flow of particles is not constant, and neither are conditions in Earth's magnetic environment. As they change, different parts of the upper atmosphere begin to glow.

From the ground, we see this as movement.

If you want to understand the whole process from the beginning, read our guide to [how the Northern Lights form].

The solar wind is always changing.

At times, disturbances from the Sun reach Earth and interact with our planet's magnetic field. More energy can then enter the system that produces the aurora.

A quiet green arc may suddenly grow brighter. New shapes can appear. Long curtains can stretch across the sky and change within seconds.

This rapid change is what people usually mean when they talk about the Northern Lights 'dancing.'

Our guide to [Northern Lights forecasts] explains how solar activity and other conditions can help you judge your chances of seeing an active display.

Yes, but not like a cloud or another solid object moving across the sky.

An aurora is light produced across a huge area of the upper atmosphere. As conditions change, different areas begin to glow while others become weaker.

To someone standing on the ground, the result can look like ribbons, waves or curtains travelling across the sky.

Sometimes the changes are slow and subtle. During an active display, the shape of the aurora can change in seconds.

Charged particles travel along Earth's magnetic field lines. This helps create the long, narrow structures often seen in the aurora.

From the ground, these structures can resemble huge curtains hanging in the sky.

As the aurora becomes more active, the curtains can develop folds, twist and brighten. Your viewing angle also changes what you see. The same auroral structure can look like a long band from one direction and something completely different from another.

Not every Northern Lights display dances across the sky.

On quieter nights, you may see a pale green arc that appears almost stationary. It can stay in roughly the same place for quite a while.

Don't assume the night is over.

Aurora activity can change quickly, and a weak arc may become brighter and more active later.

If you are travelling specifically to see the aurora, our guide to the [best time to see the Northern Lights] explains how season, darkness and weather affect your chances.

Not exactly.

Aurora forecasts can show when conditions are promising, but they cannot tell you exactly what the sky will look like at 9:47 tonight.

The forecast might suggest good conditions and the aurora may still remain fairly quiet. On another night, the display can suddenly become much more active.

Weather is another problem. A strong aurora above a thick layer of clouds is still invisible from the ground.

Forecasts are useful, but think of them as a way to understand your chances rather than a timetable for the sky.

Every display is different.

You might see a green ribbon slowly changing shape above the horizon. On a more active night, large curtains can move overhead while bright areas appear and disappear within seconds.

Sometimes the movement spreads across a large part of the sky.

That's also why seeing the Northern Lights in person is so different from simply looking at a forecast. You can choose a dark location, check the weather and wait for good conditions.

What happens next is up to the sky.