Northern Lights Colors Explained: Why Auroras Glow Green, Red, Pink and Purple

Look at a hundred aurora photos and you will see a whole paint box: electric green curtains, deep red glows, magenta domes, pink hems and violet streaks. On Halloween night 2026, a moderate geomagnetic storm put the northern lights over parts of the UK, and as usual, phone photos showed colors that many watchers had not noticed with their own eyes.

None of those colors is random. Each one comes from a particular gas, at a particular height, glowing at a particular wavelength. Once you know the code, an aurora photo becomes a readout of what the upper atmosphere was doing that night. Here is why the northern lights come in green, red, pink, purple and blue, why your phone sees more of them than you do, and how to catch the next display.

What makes the aurora glow at all

The story starts at the Sun. A steady solar wind of charged particles, plus occasional giant clouds called coronal mass ejections, stretches and jolts Earth’s magnetic field. Some of that energy is stored in the long magnetic tail on the night side of the planet and then released, sending electrons racing down magnetic field lines toward the regions around the poles.

About 100 to 300 kilometers up, those electrons slam into atoms and molecules of oxygen and nitrogen. Each collision can lift an atom or molecule into an excited state. When it settles back down, it gives off the extra energy as a photon of light with a very specific wavelength. That is the same physics as a neon sign: the gas sets the color, and the electrons supply the power.

Every gas has its own set of possible wavelengths, a spectral fingerprint. Astronomers have read those fingerprints for a long time; it is how helium was found on the Sun before anyone found it on Earth, a story told in our piece on the discovery of helium in 1868. In the aurora, the fingerprint belongs to just two main gases, and a handful of their lines do almost all the work.

A Park Service guide to the aurora by physicist Dirk Lummerzheim puts it neatly. The energy of the incoming electrons is like the voltage, and it decides how deep they reach and so which colors appear. The number of electrons is like the current, and it decides how bright the display is. The color tells you how hard the electrons hit, and where; the brightness tells you how many of them there are.

Color	Main source	Wavelength	Typical height
Green	Atomic oxygen	557.7 nm	About 100 to 200 km
Red	Atomic oxygen	630.0 nm	About 200 to 300 km and above
Pink, purple or crimson hem	Molecular nitrogen	Mix of red and blue bands	Below about 100 km
Blue or violet	Nitrogen ions (N2+)	427.8 nm	Lower edges, and sunlit tops

The color tells you how hard the electrons hit, and where; the brightness tells you how many of them there are.

Why most aurora is green

The classic green comes from oxygen atoms emitting light at 557.7 nanometers. Green dominates for two reasons. First, the oxygen at around 100 to 200 kilometers gets hit by plenty of electrons in an ordinary display. Second, human eyes are most sensitive right in the green part of the spectrum, so even a modest green glow stands out against a dark sky.

There is also a timing trick. An oxygen atom excited into the green state takes about 0.7 seconds, on average, to release its photon. That sounds instant, but in the upper atmosphere an atom can bump into a neighbor before then and lose the energy without making any light. Below about 95 kilometers the air is dense enough that this happens almost every time, which is why green aurora has a fairly sharp lower limit.

Why the top of the aurora is red

Oxygen has a second favorite color: deep red at 630.0 nanometers. The red state is far more patient. An oxygen atom lingers there for around 100 seconds, on average, before emitting. Only in the very thin air above about 200 kilometers, where collisions are rare, can an atom wait that long. So red aurora lives high up, often as a glow sitting above the green curtain.

That long wait also explains why red aurora tends to look soft and smeared. During the minute or two before the light comes out, the atom drifts and the electron stream shifts, so the fine folds of the display get blurred. Red also gets less help from our eyes, which are poor at seeing dim deep red. In most ordinary displays, the red is there but too faint to notice without a camera.

Strong storms change that. More energy goes into the high atmosphere, and the red glow can become bright enough to see. NOAA’s Space Weather Prediction Center notes that rare displays light the whole sky in deep blood red from top to bottom roughly once every ten years.

Pink, purple and that magenta hem

Sometimes a green curtain has a bright pink or crimson fringe along its bottom edge. That hem comes from nitrogen molecules, not oxygen. When the incoming electrons are especially energetic, they punch below 100 kilometers, where nitrogen molecules give off a mix of red and blue bands. Seen together, they read as pink, magenta or purple.

Nitrogen’s light is also quick. Unlike oxygen’s slow red and green, it comes out almost at once, so the hem tends to be sharp and can ripple fast. A dancing pink lower edge is a sign of a lively display, with a lot of energy reaching deep into the atmosphere.

Blue and violet: the hardest to see

Ionized nitrogen molecules give off a bluish-purple band at 427.8 nanometers, plus some deep violet. Blue tends to show up along the lower edges of very active aurora, mixing with the nitrogen red to make purple.

There is a second, stranger source of blue. Near sunrise or sunset, the top of a tall auroral ray can stick up into sunlight hundreds of kilometers overhead while the ground is dark. Ionized nitrogen in that sunlit part scatters sunlight at its own wavelengths, producing blue or violet tops on the rays. Unfortunately for watchers, human night vision struggles with deep blue and violet, so these colors are mostly a camera discovery.

Why your phone sees more color than your eyes

If you went out during a big display and saw a pale gray-green glow, then looked at your phone screen and saw vivid pink and purple, you were not imagining it. In low light, human eyes switch from cone cells, which see color, to rod cells, which are far more sensitive but essentially colorblind. Faint aurora can look like gray cloud for exactly that reason.

Phone cameras do not have that limit. In night mode, the phone holds the shutter open for a second or more, or stacks a series of short frames, collecting much more light than the eye can in an instant. Its sensor also responds to deep red and blue that our night vision handles badly. The result is that cameras pull out colors that were really there but too faint for the eye. The photographer who took the Connecticut picture above noted that the show looked much fainter to the naked eye than in the photo.

That does not mean every color in a picture is real. Heavy editing can push saturation beyond what the sky did, but the physics offers a simple sanity check: real aurora colors follow the height pattern. Green sits low, red sits above it, and pink or purple hugs the bottom edge. A photo with green floating above red is a warning sign.

Red skies far from the poles

Here is a quirk that surprises many first-time watchers. When a big storm brings aurora far south of its usual zone, the display people see is often mostly red, not green. The reason is geometry. Red aurora sits the highest, so it can be seen over the horizon from hundreds of kilometers farther away than the lower green. From a mid-latitude town, you may be looking at the top of an aurora whose green base is below your horizon.

In late October and early November 2003, during the Halloween storms, red aurora was seen as far south as the Mediterranean and Florida. Then on May 10, 2024, NOAA declared the first extreme (G5) geomagnetic storm since 2003. Over that night and the next, aurora was reported across much of Europe and North America, including places that almost never see it, such as Florida and the Gulf Coast, with reports even from Hawaii and Puerto Rico. Many of those skies were red, pink and magenta.

The biggest storm on record, the Carrington Event of 1859, produced aurora reported as far south as the Caribbean. Not every far-flung aurora is natural, either. The 1962 Starfish Prime nuclear test in space lit the sky over Hawaii with artificial aurora, as electrons from the blast spiraled along Earth’s magnetic field and struck the air.

These storms tend to cluster around solar maximum, the busy part of the Sun’s roughly 11-year cycle. NASA and NOAA announced in October 2024 that the Sun had entered its maximum period, and scientists noted that strong storms still happen during the declining phase that follows. The same active regions that make dramatic solar prominence pictures also fling out the eruptions that drive aurora.

STEVE and the picket fence: the purple ribbon that is not aurora

Since 2016, aurora chasers in Canada have been photographing a strange narrow ribbon of mauve or purple light that runs east to west across the sky, often accompanied by short green stripes beneath it like a picket fence. A Facebook group of amateur photographers named it Steve, and scientists later turned the name into an acronym: STEVE, for Strong Thermal Emission Velocity Enhancement.

When researchers analyzed its light, they found a surprise. Ordinary aurora shines in specific spectral lines, but STEVE gives off a broad, smooth spread of colors, more like a hot glowing object. A 2018 study found that its glow is not caused by charged particles raining down, the way aurora is. A 2019 study led by Boston University traced it to friction and heating in a fast river of charged particles in the upper atmosphere, a little like the glowing filament in an incandescent light bulb.

The European Space Agency’s Swarm satellites measured that river directly. During one STEVE event, the ribbon was about 25 kilometers wide and around 300 kilometers up, with a temperature near 3,000 degrees Celsius and charged gas flowing at about 6 kilometers per second. The green picket fence below, at about 95 to 150 kilometers, does involve falling electrons and oxygen’s green line, much like ordinary aurora, although some researchers think local electric fields may help power it.

STEVE usually appears closer to the equator than the main aurora and lasts from 20 minutes to about an hour. If you see a pale purple stripe south of the main show, you may have found one.

How to see the colors for yourself

The best tool is a forecast. NOAA’s Space Weather Prediction Center publishes the Kp index, a scale from 0 to 9 that tracks how disturbed Earth’s magnetic field is. NASA’s viewing guide says that at around Kp 4, aurora becomes possible in the northern United States, and SWPC notes that each step up the scale moves the equatorward edge of the aurora roughly 2 degrees of magnetic latitude toward the equator. A G-scale storm watch, from G1 for minor to G5 for extreme, is your cue to plan an outing.

Then think like a photographer:

Go dark: Get away from city lights and give your eyes 20 to 30 minutes to adapt. Use a red light to read maps and settings, since white light resets your night vision.

Look north, and up: The aurora can be visible from up to about 1,000 kilometers away from a hilltop with a clear horizon. During strong storms, check overhead and even to the south.

Pick your hours: SWPC suggests about 10 p.m. to 2 a.m. local time. Displays often come in waves, so stay out for a while. The weeks around the spring and autumn equinoxes tend to be more active, and a bright Moon will wash out faint colors.

Steady the phone: A tripod and night mode, or an exposure of several seconds on a camera, will reveal reds and purples you cannot see. Keep spare batteries warm in a pocket, since cold drains them fast.

Dress for a long wait: Aurora watching means standing still in the cold, often for hours. Warm layers, hand warmers and a hot drink make it much easier to stay out until the display peaks.

NOAA’s SWPC weekly forecast calls a G1 to G2 storm likely around November 27 and 28, 2026, when a recurring stream of fast solar wind is expected to come back around. Forecasts at that range are rough, so check again on the day.

Northern lights colors: quick answers

What is the most common aurora color?

Green, from oxygen atoms about 100 to 200 kilometers up glowing at 557.7 nanometers. It is both very common and the color human eyes pick up best in the dark.

What does a red aurora mean?

Red comes from oxygen high in the atmosphere, above about 200 kilometers. Faint red is present in many displays, but bright red you can see with your eyes usually means a strong geomagnetic storm, especially if you are far from the poles.

Why is the aurora pink or purple?

Pink and purple usually come from nitrogen molecules below about 100 kilometers, struck by especially energetic electrons. They often show up as a fringe along the bottom of green curtains.

Why does the aurora look better on my phone?

In the dark, your eyes rely on rod cells that do not see color well, while a phone in night mode gathers light for seconds and records deep reds and purples. The colors are real; they are just too faint for night vision.

Further reading