Imagine standing under the starry vault, bundled against the cold, when the sky erupts overhead. Rippling curtains, ribbons and streamers of colors across the rainbow light up the night, shimmering and majestic and all eerily silent.
That’s what it’s like to see a vivid auroral display, and being able to witness one for yourself is getting more likely every day. The sun’s been getting feisty lately, blasting out flares of radiation and burps of gas that can wash over Earth. This uptick in solar outbursts—which is an expected part of our sun’s activity cycle—boosts the chances for the occurrence of the aurora borealis, or northern lights, in the Northern Hemisphere. (In the Southern Hemisphere, the phenomenon is the aurora australis, or southern lights.) Beautiful, fantastic and still in many ways mysterious, these dancing multihued displays tend to be visible only at high latitudes, but in recent weeks they have been spotted in the Northern Hemisphere as far south as Virginia!
Many ancient peoples associated the auroras with fire, which is understandable: the sky can glow with ripples of yellow and red, as if it is itself aflame or perhaps instead reflecting some distant over-the-horizon conflagration on the ground. But the lights come in many other colors, too: green is the most common, and purple and pink can make appearances, too. Sometimes auroras can even glow an electric blue.
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
They come in many shapes as well, from curtains and sheets to streaks, undulating “dunes” and even spirals. Sometimes they seem stable and unmoving, and other times they can flicker and dance like waves that crash across the sky in seconds.
What they all have in common, besides their unearthly beauty, is their root cause: magnetism.
The sun has a fiendishly complex magnetic field created by the motions of ionized gas called plasma in its interior. The magnetic lines of force at the surface create many observable effects, including sunspots, which are dark regions where solar plasma cools and emits less light than surrounding areas. These lines also contain vast amounts of energy. If they tangle up, they can snap like rubber bands, releasing that energy as a mind-stompingly powerful solar flare—equivalent to the simultaneous detonation of billions of thermonuclear bombs—or a coronal mass ejection, which is faint in visible light but blasts away billions of metric tons of plasma from the sun at speeds upward of a million kilometers per hour.
Near the sun, these solar storms are apocalyptically intense—so strong that they can erode a planet’s atmosphere. But even on Earth, 150 million kilometers away, there can still be profound effects.
Our planet, too, has a magnetic field—and so does a cloud of plasma blasted out by a solar storm. When such outbursts hit Earth, the two magnetic fields interact in very complicated and, honestly, not terribly well-understood ways. Streams of charged particles flow along Earth’s field lines to the planet’s poles, funneling down into our atmosphere, where they strike at high speed.
These ions are like subatomic bullets that hit atoms and molecules in our upper atmosphere and rip away their electrons, which are like shrapnel. When these charged particles reconnect, a little bit of light is emitted with a color that is characteristic of the particular atom or molecule involved.
Recombining with electrons can make atomic oxygen emit red or green light, depending on atmospheric conditions. Much of Earth’s atmosphere is thick with other atoms that collide with the atomic oxygen and absorb the energy needed to emit light, so these colors are mostly seen at very high altitudes where the atmosphere is more rarified. Red can be seen at 200 kilometers or higher, and green is visible from about 100 to 200 km. Lower than that, the air is too dense for the atoms to glow, and this causes an abrupt cutoff to the green auroras at that height, which is why they commonly display a sharp lower edge.
If the particles from the sun penetrate lower into the atmosphere, they can impact nitrogen molecules, which emit light in blue and red. In a strong event, these emissions can intermix, and our eyes see this as a dazzling assortment of purple, pink, yellow and other colors. Even then, this all happens so far above our heads that the display is completely silent.
Outside of colors, the forms an aurora can take arise from exactly how a solar outburst reshapes a portion of Earth’s magnetic field. Sometimes the interaction is weak, and only a soft glow is seen. Other times the impact of the particles forms long vertical sheets, which can appear as wavy folds like a drape—in fact, these kinds of auroral shapes are called curtains. If seen from directly underneath, these curtains can seem to surround you, and perspective makes them look like they’re a series of parallel lines and waves radiating away from a single point. This is called a corona. Sometimes the magnetic field wraps around itself like a rolled-up carpet, creating a very dramatic (and somewhat rare) spiral-shaped sheet.
Because Earth’s magnetic field is dipolar like a bar magnet and aligned roughly perpendicular to our world’s rotation, geomagnetic field lines extend most prominently from the vicinity of our planet’s North and South poles. These geomagnetic lines collect incoming solar particles and channel them to polar regions, which is why vivid auroras are more common at higher latitudes. When an especially strong solar storm strikes, its particles can overflow to cascade down from the poles, creating vibrant auroras at midlatitudes. Extremely powerful solar eruptions can even spark auroras near the equator; that happened in 1859 during the very first solar storm ever detected.
Seeing an aurora depends on many factors. Although they can happen even when the sun is relatively quiet, they’re brighter during a solar storm. Several websites can alert you to such an event, including the popular SpaceWeather.com and the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center. There are apps for mobile devices that can alert you as well.
If you live in the midlatitudes, as most people in the U.S. do, and you get an alert that a solar storm is occurring, your best bet to see an aurora is to find a dark site away from city lights. It’s particularly important to have no bright lights to your north because the auroras will lie in that direction. (I used to live south of a medium-sized town, and seeing auroras was hopeless from there.) Once you’ve reached your dark site and your eyes have adapted to the darkness, first look toward the horizon; our round planet makes more distant events appear close to the ground. If you live farther north, you can try looking higher up, especially if the storm is strong.
You can try photographing the auroras if you have a decent camera and a steady mount such as a tripod. A phone camera might work as well if you have a way to hold it motionless, such as propping it up against a fence or tree (that’s worked for me when trying to photograph stars). My advice is to simply look, though, before trying to get any photographs. Just enjoy the experience!
The sun goes through magnetic cycles, with the strength of its field waxing and waning every 11 years. The next maximum was originally predicted for July 2025, but our star has already been blasting off storms that create intense auroras on Earth, suggesting that the solar cycle’s peak may occur in 2024. Even for a year or two after the peak, the sun is still capable of some pretty big events. Because of complicated physics, the best times to see auroras are usually at the equinoxes in March and September, but any time of year can have brilliant apparitions, so be alert.
I’ve never seen a strong auroral display, despite many years of trying—I’ve just never been at the right place at the right time with good weather. This cycle may finally be my chance. I’ll keep my hopes—and my eyes—high.