What if auroras could be seen everywhere?

Some nights, the sky near the poles glows green and red. These lights are called auroras.

Far from the poles, people rarely see them. What if everyone could? Let's find out where auroras come from.

On some dark nights near the North and South Poles, curtains of green, red and purple light ripple across the sky. These are auroras: the northern lights in the north and the southern lights in the south.

Many places are too far from the poles to see them often. So what if auroras could be seen everywhere, even over the equator? What would have to change? This is a thought experiment. Choose a path to explore where auroras glow, what makes their colors, and why satellite teams watch the Sun.

Auroras are light given off by Earth's upper atmosphere when energetic particles, mostly electrons, collide with its gases. They are tied to geography: NOAA's Space Weather Prediction Center describes two auroral ovals roughly centered on the magnetic poles.

This thought experiment asks what it would take for auroras to be visible from every latitude. The real evidence comes from how auroras form and from the May 2024 geomagnetic storm, which pushed them unusually far toward the equator. Anything about a world with auroras everywhere is an idea, not a forecast.

Auroras glow very, very high up in the sky.

They shine best in two rings around the top and bottom of Earth.

NOAA says auroras form about 80 to 500 kilometers above the ground. Earth's magnetic field guides the glowing particles into two ring shapes, called ovals, one around each magnetic pole.

The best place to watch is under those ovals, between about 60 and 75 degrees of latitude. There, auroras can be seen on more than half of the nights in a year. You also need a clear, dark sky, so in summer, when the Sun barely sets near the poles, auroras are hard to see.

According to NOAA's Space Weather Prediction Center, auroras typically form 80 to 500 km above Earth's surface. Electrons energized in the night-side tail of the magnetosphere follow magnetic field lines down toward the polar regions, so the light appears in two ovals approximately centered on the magnetic poles.

Under the ovals, between about 60 and 75 degrees latitude, auroras are visible on more than half of the nights of a year. Viewing still needs clear, dark skies: in summer at auroral latitudes the midnight Sun prevents observations. NOAA notes that protons also cause aurora, but it is faint and diffuse and usually hard to see by eye.

Sometimes the Sun sends a big burst of particles. Then the aurora rings grow bigger.

People far from the poles can see the lights too!

The aurora ovals don't stay the same size. NOAA explains that during big geomagnetic storms, which are disturbances in Earth's magnetic field caused by the Sun, the ovals spread away from the poles. In major storms, auroras can be seen over most of the United States.

To see auroras everywhere, even at the equator, the ovals might have to spread much farther than in any storm described here. That is an idea, not a prediction: no source says how strong a storm would need to be.

Auroral ovals expand equatorward when geomagnetic activity rises. NOAA notes that in major storms aurora can be seen over most of the United States, and during large events as far south as the U.S., Europe and Asia; in very large events, even farther from the poles.

For auroras to be visible from every latitude, the ovals might have to expand well beyond any case described here. This lab does not model the magnetosphere, so it cannot say what storm strength that would take; treat the equator scenario as an idea built on the observed pattern.

The Sun sends out tiny bits called particles. Earth has a magnetic field around it, like an invisible bubble.

The bubble steers some particles to the poles. There they bump into the air and make it glow.

The Sun sends out more than light and heat. It also streams out tiny particles. NASA explains that Earth's magnetic field shields us from most of them. During a solar storm, though, some particles get trapped in the field, gain energy and travel down the field lines near the poles.

When they hit gases high in the air, those gases give off light. NASA says oxygen glows green and red, and nitrogen glows blue and purple. NOAA compares it to how a neon light works. Because the field lines lead to the poles, that is where the lights gather.

NOAA describes the mechanism: electrons accelerated in the magnetosphere's night-side tail and along auroral field lines follow Earth's magnetic field into the upper atmosphere, where they collide with oxygen and nitrogen atoms and molecules. The collisions excite those particles to higher energy states, and when they relax they release light, much as a neon sign does. NASA Space Place notes oxygen emits green and red light and nitrogen blue and purple.

The field decides the location: NOAA says Earth's magnetic field guides the electrons so that the aurora forms two ovals around the magnetic poles, and when space weather activity increases, the aurora extends toward the equator.

In May 2024, the Sun sent out a big storm. Auroras glowed in places that rarely see them.

People took photos with their phones and shared them with scientists.

In early May 2024, the Sun launched a string of big flares and at least seven giant clouds of particles toward Earth. NASA says it was the strongest solar storm to reach Earth in two decades. Auroras were seen at unusually low latitudes, including the southern United States and northern India.

Thousands of reports were sent to Aurorasaurus, a citizen science project funded by NASA. A NASA scientist noted that even ordinary phone cameras now pick up aurora colors well. Before the storm, NOAA warned satellite and power grid operators so they could prepare.

From May 7 to 11, 2024, multiple strong flares and at least seven coronal mass ejections headed for Earth; NASA reports they arrived from May 10 and drove a G5 geomagnetic storm, the top of the scale, last reached in 2003. Auroras were reported as low as 26 degrees magnetic latitude, and NASA says the event may rank among the lowest-latitude aurora sightings in five centuries, though scientists were still assessing that.

NOAA's Space Weather Prediction Center alerted power grid and commercial satellite operators in advance, and some NASA spacecraft powered down instruments; ICESat-2 entered safe mode, likely because of extra atmospheric drag. Citizen reports to Aurorasaurus, including non-sightings, help map the storm's reach.