The science of the northern lights, and why the sky has been putting on such a show

There are few sights in nature that stop people in their tracks quite like the aurora. Great curtains of green and violet light ripple silently across the night sky, shifting and folding as though the heavens themselves were breathing. It feels almost magical, yet it is pure physics.

In the last couple of years, these displays have been unusually generous, appearing in places that almost never see them. To understand why, you have to follow a chain of events that begins ninety three million miles away, on the surface of the sun.

A gift from the sun

Our sun is not a calm, steady ball of fire. It constantly hurls a stream of charged particles out into space, a flow known as the solar wind. Now and then it also erupts more violently, flinging vast clouds of magnetized plasma outward in what scientists call coronal mass ejections.

When one of those clouds is aimed at us, it sweeps across the ninety three million mile gap and slams into our planet a day or two later. The energy it carries is the raw fuel for every auroral display, and the bigger the eruption, the more spectacular the potential show.

Steered by an invisible shield

If those particles simply hit us head on, life would be in trouble. Luckily, the Earth is wrapped in a magnetic field, an invisible shield generated deep in our planet's molten core that deflects most of the incoming onslaught safely around us.

That shield is not uniform, though. It funnels a portion of the particles down toward the north and south magnetic poles, which is exactly why auroras cluster near the top and bottom of the globe. In the north we call them the aurora borealis, and in the south the aurora australis.

Why the colors change

The light itself is born when those particles crash into the gases of our upper atmosphere. They slam into atoms of oxygen and nitrogen and transfer their energy, briefly exciting them. When the atoms settle back down, they release that energy as a tiny flash of colored light.

Which color you see depends on which gas is glowing and how high up it is. Oxygen tends to produce the familiar vivid greens lower down and deep reds higher in the sky, while nitrogen contributes the blues, purples, and delicate pinks that fringe the brightest curtains.

The sun's eleven year heartbeat

The reason the shows come and go over the years is that the sun runs on a rhythm. Roughly every eleven years its activity swells to a peak and then fades again, a pattern known as the solar cycle, and we recently passed through one of those peaks.

Scientists mark the current cycle as number twenty five, and its maximum arrived around late 2024. During a solar maximum the sun is freckled with more sunspots and unleashes far more eruptions, which is why auroras have been so frequent and so bright of late.

A rare treat at lower latitudes

The most dramatic moments come from powerful geomagnetic storms. In 2024 the planet was hit by the strongest such storm in decades, rated at the top of the scale, and it pushed the glowing lights far south of their usual haunts near the pole.

People who had never dreamed of seeing the aurora suddenly found it glowing above their own backyards, well into the middle latitudes. Such storms are rare, but during an active sun they become dramatically more likely, turning a polar privilege into a much wider gift.

How to catch them yourself

If you want to see the lights, a few simple things stack the odds in your favor. Get far away from city glare, find a clear night with a wide view toward the north, and let your eyes adjust to the dark for a good twenty minutes or so.

It also pays to watch the space weather forecasts, which predict when a solar storm is due to arrive. The sun is now easing out of its peak, but strong flare ups can still occur for the next couple of years, so the curtains have not closed on the show just yet.