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01 — Overview
What Causes the Northern Lights?
Long before science had an explanation, people looked up and tried to make sense of them. Many Native American tribes believed the northern lights were the spirits of ancestors dancing in the sky. The Menominee of Wisconsin saw them as torches carried by great giants to light their way as they speared fish. The Fox tribe believed they were the ghosts of slain enemies, restless and threatening. For centuries across Arctic and subarctic cultures, the lights were simply a message.
Science has since offered its own explanation, one no less astonishing. The northern lights, aurora borealis, are caused by charged particles from the Sun colliding with gases in Earth's upper atmosphere. Guided by Earth's magnetic field toward the poles, those particles slam into oxygen and nitrogen atoms at altitudes of 62 to 186 miles (100 to 300 km), transferring energy that is released as light. That light is the aurora. The full story involves the Sun, Earth's invisible magnetic shield, quantum physics, and a feedback loop between our star and our planet that has been running for billions of years.
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250–500 mi/s
Solar Wind Speed
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11 years
Solar Cycle Length
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62–186 mi
Aurora Altitude
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02 — The Sun's Role
The Sun's Role: Solar Wind and Solar Storms
The Sun is not a static ball of fire. It constantly ejects a stream of charged particles, mostly electrons and protons, outward in all directions at 250 to 500 mi/s (400 to 800 km/s). This is the solar wind, and it bathes the entire solar system in a continuous flow of plasma. Earth sits in that flow, 93 million miles (150 million km) from the source, receiving its share of the particle stream around 1 to 3 days after those particles left the Sun.1
Solar flares are intense flashes of radiation and Coronal Mass Ejections (CMEs) are enormous clouds of magnetized plasma hurled into space, sometimes containing billions of tonnes of material. When a CME is directed toward Earth it can compress Earth's magnetic field, drive vast currents through the upper atmosphere, and trigger geomagnetic storms. Strong geomagnetic storms lead to the brightest, most widespread auroras.
Solar activity itself follows an approximately 11-year cycle. At solar maximum, the peak of activity, sunspot numbers rise, flares become more frequent, and CMEs are more common and powerful. We entered Solar Cycle 25's maximum around 2024 to 2025, which directly explains the extraordinary aurora activity seen globally during that period.
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Solar wind is not a metaphor. It is a real wind of particles streaming past Earth at up to 500 mi/s (800 km/s) every second of every day.
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03 — Earth's Magnetic Field
Earth's Magnetic Shield
Without its magnetic field, Earth would be a very different, and likely uninhabitable, place. The magnetosphere, the vast magnetic bubble that surrounds and protects Earth, deflects the bulk of the incoming solar wind, protecting the surface from the full force of particle radiation. The magnetosphere is why Earth has an atmosphere at all. Mars, for example, lost most of its atmosphere billions of years ago in part because its magnetic field collapsed, allowing the solar wind to gradually strip atmospheric particles away.
However, the magnetosphere is not a perfect shell. At the poles, magnetic field lines converge and dip toward Earth's surface, exposing a weakness in the shield. This allows charged particles from the solar wind to funnel down along these field lines and enter the upper atmosphere. This is also why auroras appear in oval-shaped rings around the magnetic poles, and not everywhere at once.2
During strong geomagnetic storms, the magnetosphere is compressed and distorted by the incoming CME. The auroral ovals expand and spread from the polar regions toward lower latitudes. In extreme events, auroras have been visible from the tropics. The mechanism driving this expansion was formalized in 1961 when physicist James Dungey proposed the concept of magnetic reconnection: the Sun's magnetic field temporarily merging with Earth's at the dayside magnetopause, opening a channel for particles to pour in.3
04 — The Colors
How the Colors Are Made
Aurora colors are not random. Each color is a direct signature of which gas is being excited and at what altitude.4 When a charged particle collides with an atmospheric atom, it bumps an electron to a higher energy level. When that electron drops back down, it releases the energy as a photon of a specific wavelength, a specific color.
| Color |
Gas |
Altitude |
Notes |
| Green |
Oxygen |
62–93 mi |
Most common aurora color; brightest and most visible to the naked eye |
| Red |
Oxygen |
124–186 mi |
High-altitude oxygen; rarer, often appears as a red glow above green bands |
| Blue / Violet |
Nitrogen |
Below 62 mi |
Ionized nitrogen at lower altitudes; often appears at aurora bases |
| Pink / Magenta |
Nitrogen + Oxygen |
~62 mi |
Mix of nitrogen emissions and green oxygen at the lower aurora boundary |
| Purple |
Nitrogen |
Very low |
Seen during very intense activity; often in auroral curtain edges |
Green is overwhelmingly the most common color because oxygen at 62 to 93 miles (100 to 150 km) is the most abundant target in the aurora zone, and the 557.7 nm green emission is particularly efficient. Red auroras, the same oxygen atom but at much higher altitudes where it stays in an excited state longer, are more rare and were particularly striking during the 2024 superstorm, visible at latitudes where green auroras alone were already unusual.
05 — Viewing
Where and When to See Them
Under normal solar conditions, auroras are confined to the auroral oval, a band roughly centered on the magnetic poles at latitudes between 65° and 72° north and south. The best viewing locations are therefore in the far north: northern Norway, Iceland, northern Canada, Alaska, and northern Finland and Sweden. The southern equivalent, aurora australis, is visible from southern Chile, Argentina, and Antarctica.
The optimal conditions for aurora viewing require three things to align: geomagnetic activity (the higher the Kp index, the better, on a scale from 0 to 9 measuring geomagnetic disturbance), darkness (no sunlight, ideally no moon), and clear skies. The equinoxes, March and September, tend to produce slightly more geomagnetic activity on average, making spring and autumn statistically the best seasons despite the common assumption that deep winter is best.
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Fast Fact
Cameras often capture aurora colors more vividly than the naked eye because camera sensors are more sensitive to certain wavelengths, particularly red, at low light levels. An aurora that appears faintly white or pale green to the eye can look brilliantly multicolored in a long-exposure photo.
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06 — 2024 Superstorm
The 2024 Superstorm: Why Auroras Went Global
In May 2024, a cluster of powerful solar flares and associated CMEs triggered the strongest geomagnetic storm since the Halloween storms of 2003. Auroras were visible across Europe as far south as Spain, Italy, and Greece. In the United States, they were seen in Texas, Florida, and California. In the southern hemisphere, auroras appeared over Australia and New Zealand.5
The storm was caused by Active Region 13664, a cluster of sunspots that produced at least five X-class flares and several fast CMEs in quick succession. The compounding effect of multiple CMEs arriving together created a particularly intense and sustained geomagnetic disturbance where millions of people who had never seen an aurora in their lives stepped outside and watched the sky glow red, green, and purple.
The event was a scientific opportunity as well as a spectacle. Space weather researchers were able to study the effects of an extreme storm on power grids, satellite navigation systems, radio communications, and high-frequency aviation routes, all of which showed measurable disruption during the storm's peak. It served as a reminder that aurora activity is not merely beautiful but that geomagnetic storms at this scale have real consequences for modern infrastructure.6
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The most powerful geomagnetic storm in recorded history, the Carrington Event of 1859, set telegraph wires on fire and produced auroras visible from the tropics. A storm of that magnitude today would cause trillions of dollars in infrastructure damage.
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07 — FAQ
Northern Lights FAQ
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Do auroras make any sound?
Reports of aurora sounds, crackling, hissing, clapping, have existed for centuries across Arctic cultures. For a long time scientists were skeptical, since the aurora occurs at altitudes where air is too thin to carry sound to the surface. Research published in 2012 by Finnish scientists confirmed the sounds are real. They originate from electrostatic discharge near the ground during strong geomagnetic events, caused by temperature inversions in the lower atmosphere interacting with charge differences created by the storm above. The sounds are not produced by the aurora itself, but are triggered by it.
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Is aurora borealis the same as aurora australis?
Yes, they are the same phenomenon occurring simultaneously at both poles. Aurora borealis appears in the northern hemisphere; aurora australis in the southern. Because both are driven by the same geomagnetic event, they are nearly mirror images of each other, appearing at the same time and often in similar shapes. The southern lights receive far less attention simply because the aurora oval over the southern pole lies mostly over Antarctica and the Southern Ocean, with very little accessible landmass beneath it.
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Can auroras be predicted?
Yes, with moderate accuracy and limited lead time. NOAA's Space Weather Prediction Center issues aurora forecasts based on solar observations, CME detection, and real-time solar wind data from the DSCOVR satellite positioned at the L1 Lagrange point between Earth and Sun. When a CME is detected heading toward Earth, forecasters can issue a geomagnetic storm warning 1 to 3 days in advance. Within hours of a CME arrival, the Kp index updates in near-real time, allowing aurora watchers to know whether conditions are favorable.
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Do other planets have auroras?
Every planet with both a magnetic field and an atmosphere has auroras. Jupiter's are the largest and most powerful in the solar system, driven partly by its moon Io, whose volcanic eruptions inject charged particles directly into Jupiter's magnetic field. Saturn, Uranus, and Neptune also have auroras. Even some moons, including Ganymede, the only moon with its own magnetic field, produce their own auroral activity. The James Webb Space Telescope has observed auroras in the atmospheres of brown dwarfs beyond our solar system.
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Why do auroras move and dance?
The rippling, curtain-like motion of auroras reflects the constantly shifting structure of Earth's magnetic field lines under the pressure of the solar wind. As the flow of particles varies, gusting and ebbing like any wind, the regions of particle precipitation shift and intensify. Substorms, identified by physicist Syun-Ichi Akasofu in 1964, are the discrete events within a geomagnetic storm that produce the sudden brightenings and rapid movements: bursts of energy stored in Earth's magnetic tail releasing explosively and lighting up new regions of the auroral oval within minutes.7
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08 — Sources
Sources and References
All factual claims in this article are drawn from peer-reviewed research and primary scientific sources. Editorial analysis and synthesis are original.
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1
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Mason, C.W. "The Mythology of the Northern Lights." Journal of American Folklore, 24(91), 1–18 (1911). A foundational survey of aurora mythology across Native American and Arctic cultures, documenting tribal interpretations of the northern lights including the Menominee belief in giant torchbearers and the Fox tribe's association of the lights with the spirits of slain enemies, among the earliest scholarly records of indigenous aurora traditions in North America.
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2
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Pulkkinen, T. "Space Weather: Terrestrial Perspective." Living Reviews in Solar Physics, 4(1), 1–60 (2007). A comprehensive review of the Sun-Earth connection covering the solar wind, magnetospheric physics, geomagnetic storms, and auroral dynamics — including the role of the magnetosphere in shielding Earth and funneling particles toward the poles to produce auroras.
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3
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Dungey, J.W. "Interplanetary Magnetic Field and the Auroral Zones." Physical Review Letters, 6(2), 47–48 (1961). Dungey's two-page landmark paper introducing the concept of magnetic reconnection at the dayside magnetopause — the mechanism by which the interplanetary magnetic field merges with Earth's, opening a pathway for solar particles to enter the magnetosphere and drive auroral activity.
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4
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Chamberlain, J.W. Physics of the Aurora and Airglow. Academic Press, New York (1961). The classical reference on the spectroscopy and photochemistry of aurora emissions — establishing the physical basis for each aurora color including the 557.7 nm green oxygen line, the 630.0 nm red oxygen line, and the blue-violet nitrogen emissions at lower altitudes.
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5
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Knipp, D.J. et al. "The May 2024 Geomagnetic Superstorm: Updates and Impacts." Space Weather, 22(9), e2024SW004113 (2024). Analysis of the May 10–12, 2024 G5 geomagnetic storm — the strongest since November 2003 — including the solar source region AR13664, the sequence of CME arrivals, the Kp=9 peak, and documented impacts on infrastructure, navigation systems, and aurora visibility at historically low latitudes worldwide.
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6
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Cliver, E.W. & Svalgaard, L. "The 1859 Solar-Terrestrial Disturbance and the Current Limits of Extreme Space Weather Activity." Solar Physics, 224(1–2), 407–422 (2004). Historical and physical analysis of the Carrington Event — the most intense geomagnetic storm in the observational record — establishing its parameters and modeling the consequences of a similar event for modern power grid, satellite, and communication infrastructure.
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7
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Akasofu, S.-I. "The development of the auroral substorm." Planetary and Space Science, 12(4), 273–282 (1964). Akasofu's original description of the auroral substorm — the discrete explosive brightening and rapid expansion of the aurora that produces the rippling, dancing motion characteristic of active displays — establishing the substorm as the fundamental unit of auroral dynamics within a geomagnetic storm.
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Guide to Space — The Rise Daily
This article is part of an ongoing educational series on space science published by therisedaily.com. Editorial content is original. All factual claims are sourced and footnoted above.
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