Aurora Borealis: Complete Guide to the Northern (and Southern) Lights
From the physics of solar wind colliding with Earth's magnetic field to practical advice on where to stand and when to look up, this is everything you need to chase — and understand — one of nature's most spectacular light shows.
The aurora borealis — northern lights — has captivated humanity for millennia. Ancient Norsemen saw it as the shimmer of Valkyries' shields. Today we know it as the visible signature of our planet's magnetic shield deflecting a constant bombardment of charged particles from the Sun. We are currently living through one of the best aurora-viewing periods in two decades, with Solar Cycle 25 reaching its maximum in 2025–2026 and producing some of the strongest geomagnetic storms since the early 2000s. If you have ever wanted to see an aurora, the window is open right now.
What Causes Auroras: Solar Wind Meets the Magnetosphere
The Sun continuously blasts charged particles — mostly protons and electrons — outward in all directions as the solar wind. Earth is protected from this particle stream by its magnetic field, the magnetosphere, which deflects most of the flow around the planet like a boulder diverting a river. But the magnetosphere is not a perfect shield. At the polar regions, magnetic field lines converge and dip into the atmosphere, and here the magnetosphere has a controlled vulnerability: charged particles can funnel down along these field lines and collide with atoms in the upper atmosphere at altitudes between roughly 100 and 300 kilometers.
When an energetic electron or proton collides with an atom of oxygen or nitrogen in this altitude range, the atom absorbs the energy and its electrons jump to higher energy states. When those electrons fall back to their ground states, they release the absorbed energy as photons of light — the aurora. The process is essentially the same as that in a neon sign or fluorescent lamp, just operating at planetary scale in Earth's own upper atmosphere.
The shape and motion of auroras — the characteristic curtains, rays, arcs, and coronas — reflect the structure of the magnetic field lines along which the particles travel. Rapid flickering and dancing movements arise because the particle flow is constantly varying in intensity and direction. Auroras appear in an oval band around each magnetic pole, the auroral oval, which expands equatorward when geomagnetic activity is high. During major geomagnetic storms, auroras have been seen as far south as Texas, Spain, and northern China.
Aurora Colors and What Causes Them
The color of an aurora depends on which atmospheric gas is being excited and at what altitude — and therefore what atmospheric pressure — the collision occurs. The most common aurora color, the vivid green that appears in most photographs, is produced by atomic oxygen at altitudes of roughly 100 to 150 kilometers. The specific green wavelength — 557.7 nanometers — comes from a quantum transition in oxygen that is technically "forbidden" (very slow to occur) but can complete before the excited atom is disturbed at these relatively low pressures.
At higher altitudes, above about 200 kilometers, atomic oxygen produces red rather than green light. Red auroras are rarer because the gas density is low, meaning fewer collisions produce the effect, but during strong geomagnetic storms, vivid red aurora curtains can appear above the green, creating spectacular two-tone displays. Nitrogen molecules produce blue and purple hues, most visible at lower altitudes and often appearing as a blue fringe at the base of aurora curtains where the particles are penetrating deepest into the denser atmosphere. Pink and magenta tones can appear where the green and blue zones overlap. The mixture of these components creates the rainbow-like variety of colors seen during particularly active events.
Why 2025–2026 Is an Exceptional Aurora Period
The Sun follows an approximately 11-year activity cycle between solar minimum (few sunspots, quiet solar wind) and solar maximum (many sunspots, frequent flares and coronal mass ejections). Solar Cycle 25, which began in December 2019, reached its predicted maximum in 2025 and is tracking well above the official NOAA/NASA forecast — making it one of the most active cycles since Solar Cycle 23 peaked in 2001. The elevated activity translates directly into more frequent and more powerful geomagnetic storms at Earth.
The key events that produce the strongest auroras are coronal mass ejections (CMEs) — enormous eruptions of magnetized plasma from the Sun's corona that can contain billions of tons of charged particles traveling at up to 3,000 kilometers per second. When a CME aimed toward Earth arrives, typically 1–3 days after launch, it compresses Earth's magnetosphere and can trigger geomagnetic storms measured on the Kp scale from 0 (quiet) to 9 (extreme). A Kp of 5 constitutes a G1 minor geomagnetic storm — visible aurora in Alaska and northern Scandinavia. A Kp of 7–8 (G3–G4) pushes the auroral oval into the northern United States and central Europe. The historic Carrington Event of 1859 would have pegged the scale at 9. In May 2024, a sequence of X-class solar flares and CMEs produced a G5 extreme geomagnetic storm — the strongest in 21 years — generating auroras visible across the continental United States, Europe, Australia, and as far south as Mexico and the Canary Islands.
During solar maximum, such strong events occur multiple times per year rather than once per decade. Forecasters at NOAA's Space Weather Prediction Center and the ESA Space Weather Service monitor the Sun around the clock and can typically give 1–3 days of warning when an Earth-directed CME is on its way. The window is short but actionable.
The Kp Index: Your Aurora Forecast Number
The Kp index is the primary tool aurora chasers use to assess activity. It is a global measure of geomagnetic disturbance updated every three hours, running from 0 (completely quiet) to 9 (extreme storm). For aurora viewing, think of it as a threshold number: you need to be at or above a certain Kp level to see the aurora from your latitude. From the far north — Tromsø, Fairbanks, Reykjavik — even Kp 2–3 is enough on a dark, clear night. From the northern United States or central Europe, you typically need Kp 5 or higher. From the southern US or the Mediterranean, Kp 7–8 is required for a chance at the horizon glow.
The Kp index is reported alongside the Bz component of the interplanetary magnetic field — the orientation of the solar wind's magnetic field as it approaches Earth. When Bz is strongly negative (southward), it couples efficiently with Earth's magnetic field and drives stronger geomagnetic activity even from a moderate solar wind event. Conversely, a strong CME with northward Bz may produce a surprisingly quiet storm. Real-time monitoring apps track both values.
Best Places to See Auroras
Northern Hemisphere: Aurora Borealis Hotspots
The ideal aurora-viewing locations are within the auroral oval — a band centered roughly 65–72 degrees magnetic latitude that represents the zone of most frequent activity. Tromsø, Norway (69°N) is the world's most popular dedicated aurora-tourism destination, offering professional guided tours, excellent infrastructure, and average of 200 clear nights per year. It sits within the auroral oval, meaning auroras occur here even at low Kp levels. Abisko, Sweden, in the rain shadow of the Norwegian mountains, has some of the clearest skies in northern Scandinavia and hosts the famous Aurora Sky Station.
Iceland offers a unique combination of geologically spectacular landscapes (glaciers, waterfalls, lava fields) and excellent aurora access — Reykjavik itself can display auroras on active nights, though darker areas outside the city are preferable. The Snæfellsnes Peninsula and the Westfjords are particularly remote and dark. Fairbanks, Alaska, is the premier North American site, sitting directly beneath the auroral oval and offering multi-night aurora tour packages with statistics showing aurora visible on approximately two thirds of nights. The Yukon — particularly Kluane National Park and areas around Whitehorse — combines darkness with dramatic mountain scenery. Finnish Lapland, centered on Saariselkä and Kakslauttanen (famous for its glass igloos), and Canadian destinations such as the Northwest Territories (Yellowknife) round out the top tier.
Southern Hemisphere: Aurora Australis
The aurora australis — southern lights — is the exact counterpart of the aurora borealis, occurring simultaneously at the southern magnetic pole during the same geomagnetic storms. Because the southern auroral oval passes over mostly ocean and Antarctica, viewing locations are fewer. The best accessible sites are the southern tip of New Zealand's South Island (Invercargill, Queenstown, the Catlins coast), the Falkland Islands, and southern Tasmania (Bruny Island, Cockle Creek). During strong G4–G5 storms, auroras have been photographed from the southern coasts of mainland Australia and Argentina. Antarctica itself offers the most intense displays but requires expedition access.
Best Times: Months, Hours, and the Equinox Effect
Auroras require two things simultaneously: sufficient geomagnetic activity and a dark sky. This means no aurora during Arctic or Antarctic summer when the sky never fully darkens. The optimal viewing months in the northern hemisphere are September through March, with October and March being statistically the most active due to a phenomenon called the Russell-McPherron effect. Around the equinoxes, the geometry of Earth's orbit relative to the solar wind's magnetic field creates conditions that allow geomagnetic storms to develop more easily even from moderate solar wind. Many seasoned aurora chasers prioritize equinox periods above all others.
Within a given night, aurora activity peaks around local magnetic midnight — roughly speaking, the point when the Sun is on the opposite side of Earth from your location, which in most northern locations corresponds to roughly 11 PM to 1 AM local time, though this varies with longitude relative to your time zone's center. Auroras can and do appear at other hours, particularly during strong storms, but planning a watch around magnetic midnight maximizes your chances.
How to Photograph Auroras
Aurora photography has become far more accessible in the smartphone era — modern flagship phones with computational night mode can capture auroras that the naked eye can barely see, and can even reveal colors (particularly reds and purples) invisible to human vision due to the eye's poor color sensitivity in low light. That said, a dedicated camera on a tripod still produces superior images and gives you much more control. Here are the key settings:
Use a wide-angle lens with the largest aperture available — f/1.8 to f/2.8 is ideal. Mount the camera on a sturdy tripod and use a remote shutter release or the camera's self-timer to eliminate vibration. Set focus manually to infinity (or use live view to focus on a bright star). For ISO, start at 800–1600 for a bright aurora and increase to 3200–6400 for a faint one, accepting that higher ISO means more digital noise. Shutter speed depends on aurora activity: for slow-moving, diffuse auroras, 10–25 seconds works well; for rapidly dancing curtains or rays, drop to 2–5 seconds to capture motion rather than blur it. Shooting in RAW format preserves maximum dynamic range for post-processing. Dress for extreme cold — your hands and battery will both drain faster than you expect.
Composition matters as much as exposure. Including foreground elements — a snow-covered cabin, a reflection in a lake, silhouetted mountains — transforms an aurora snapshot into a photograph. The rule of thirds applies: place the aurora's most intense region in the upper third of the frame, with landscape filling the lower portions.
Aurora Alert Apps and Space Weather Resources
SpaceWeatherLive (available as a website and mobile app) is the most comprehensive free resource for aurora chasers, displaying real-time Kp index, solar wind speed and density, the critical Bz component, and a live auroral oval map showing where the oval currently sits. It offers push notification alerts when the Kp index exceeds a threshold you set. My Aurora Forecast and Aurora Alerts (iOS and Android) are more user-friendly apps that translate the Kp data into a local probability percentage for your specific GPS location, making it easy to assess on any given night. NOAA's official Space Weather Prediction Center (swpc.noaa.gov) provides the authoritative source for forecasts and the 3-day CME arrival forecast when relevant events occur.
For the ultimate early warning, follow the ACE/DSCOVR satellite data feeds — these space weather satellites orbit the L1 Lagrange point, roughly 1.5 million kilometers sunward of Earth, and can measure the incoming solar wind about 15–60 minutes before it arrives. This is your final warning before an aurora storm hits. Apps like SpaceWeatherLive update this data in near-real-time.
Auroras from the ISS and from Space
Astronauts aboard the International Space Station have a uniquely privileged view of auroras: they orbit at roughly 400 kilometers altitude — within or just above the auroral layer itself — and travel the entire globe every 90 minutes, crossing through the auroral ovals on nearly every orbit during active periods. ISS crews have published thousands of aurora photographs over the station's 25 years of continuous occupation, and these images reveal structures impossible to see from the ground: the full 3D shape of aurora curtains extending below the spacecraft, the curvature of the auroral oval against Earth's limb, and simultaneous views of aurora borealis and aurora australis occurring in perfect conjugate symmetry at opposite poles.
NASA's aurora photography from the ISS has also served as a scientific calibration tool, helping researchers verify models of the auroral oval's extent during various storm levels. Some of the most dramatic ISS aurora images, taken during the May 2024 G5 storm, show the auroral oval expanded so far equatorward that the glow was visible even at mid-latitudes from orbit. Future commercial space stations will give more private travelers and researchers their own chance to view the lights from above — a perspective that fundamentally changes your understanding of this phenomenon as a planetary-scale event rather than a local display.