Long before Iceland’s first settlers arrived the northern lights were already dancing. From the time of dinosaurs and wandering Vikings to the age of satellites and smartphones, the aurora borealis has painted the skies above the North in glowing waves. But what exactly causes this ethereal display to appear over places like Iceland, where the night sky often feels alive? Let’s take a closer look at the science behind the magic.
What Are the Aurora Borealis?
The aurora borealis, commonly known as the Northern Lights, is a visible manifestation of space weather. It occurs when charged particles from the Sun collide with atoms and molecules in Earth’s upper atmosphere, producing light through a process called ionization. The phenomenon is not just beautiful — it’s a complex interaction between solar physics, magnetospheric dynamics, and atmospheric chemistry.
Let’s unpack what that actually means.
Solar Origins: The Role of the Sun
The story begins with the Sun’s corona, the outermost layer of its atmosphere. This region is extremely hot—over a million degrees Celsius—and constantly releases a stream of charged particles known as the solar wind. This wind consists primarily of electrons, protons, and alpha particles traveling at speeds between 300 and 800 km/s [1] (about 1 million to 1.8 million mph).
Occasionally, the Sun releases a more intense burst of plasma called a coronal mass ejection (CME). These are massive clouds of magnetic field and plasma that can enhance auroral activity if they reach Earth.
Earth's Magnetic Shield: The Magnetosphere
Earth is protected by its magnetic field, known as the magnetosphere, which deflects most of the incoming solar wind. However, near the magnetic poles, the field lines dip inward toward the planet, creating a funnel-like path that allows charged particles to penetrate the upper atmosphere.
These particles spiral along the magnetic field lines and enter the atmosphere around 80 to 500 kilometers above the Earth's surface, primarily near the auroral ovals — ring-shaped zones around the magnetic poles.
Collision Course: How Light is Produced
Once these solar particles enter the upper atmosphere, they collide with gas atoms and molecules, mainly oxygen (O₂ and O) and nitrogen (N₂).
These collisions transfer energy to the atmospheric gases, exciting their electrons. When those electrons return to their normal (ground) state, they release photons — particles of light.
- Oxygen atoms emit green light at about 557.7 nm (the most common auroral color), and red light at 630.0 nm at higher altitudes.
- Nitrogen molecules emit blue and purple light depending on the energy level of the incoming particle.
This process is a type of photon emission, specifically a form of atomic fluorescence, where light is produced not from heat but from the release of absorbed energy.
Why Are the Northern Lights Visible in Iceland?
Iceland’s northern latitude makes it one of the best spots on the planet to see the aurora. The country sits just south of the Arctic Circle and right in the so-called auroral oval — a ring-shaped zone around Earth’s magnetic poles, found between 65° and 75° magnetic latitude [2], where auroral activity is the most frequent and intense. This means that when there’s enough solar activity, the lights are often visible during the northern light months in Iceland from late August to mid-April. Surprisingly during the darker months there are even places to go in Reykjavik to see the Northern Lights, even despite the heavy light pollution.
But what exactly causes the auroras here?
It’s all about solar wind and geomagnetic activity. When the sun sends out a coronal mass ejection (basically a massive belch of charged particles), those particles slam into Earth’s magnetosphere. The stronger the storm, the more dramatic the light show. Iceland, with its dark skies and low light pollution in rural areas, is perfectly positioned to catch the action.
Best visibility typically occurs:
- From late August to mid-April
- Between 10 PM and 2 AM
- On geomagnetically active nights, especially after solar storms
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How Long Do the Northern Lights Last?
The northern lights don’t run on a clock, but here's what we know.
Individual auroral displays can last anywhere from a few minutes to a few hours. It all depends on solar wind strength, geomagnetic activity, and — you guessed it — the weather.
In Iceland, I’ve stayed up late and seen the aurora pop up just after midnight and fade before my tea even cooled down. But I’ve also watched them dance across the sky for nearly two hours straight.
What Aurora Colors Can You See in Iceland?
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Altitude Range
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Atmospheric Gas
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Emitted Light Color
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Notes
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100–300 km
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Oxygen (O)
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Green (most common)
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Most intense and visible to the naked eye
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300–400 km
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Oxygen (O)
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Red
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Rare and often faint
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100 km
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Nitrogen (N)
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Pink or dark red
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Rare but appears at the lower edge of an aurora.
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> 100 km
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Nitrogen (N)
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Blue and purple
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Common during strong geomagnetic storms
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While green is the most iconic color of the aurora borealis, especially in Iceland, the Northern Lights can actually display a full range of colors depending on atmospheric conditions, particle energy, and altitude. These variations are rooted in physics — specifically, in how charged particles from the sun interact with gases in Earth’s upper atmosphere.
Green is by far the most common color you’ll see, and it comes from collisions between solar particles and atomic oxygen at altitudes of about 100 to 300 kilometers (60-90 miles) [3]. These collisions release photons at a wavelength of 557.7 nanometers, which falls in the green part of the spectrum. The high efficiency of this reaction, combined with the abundance of atomic oxygen at these heights, is why green dominates most auroral displays in Iceland.
Red auroras come from the same atomic oxygen but at higher altitudes — 300 to 400 km (185-250 miles), according to the CSA. Here, the thinner air allows excited atoms to hold onto energy longer before releasing it as red light at 630.0 nanometers [4]. Red auroras are rarer because the process is less efficient and more easily disrupted by atmospheric collisions at lower altitudes.
During strong geomagnetic storms, the aurora can also dip lower into the atmosphere, triggering emissions from molecular nitrogen. These produce blue and purple light at altitudes below 100 kilometers. Our eyes are less sensitive to these shorter wavelengths in the dark, which is why these colors often appear faint in person but show up brilliantly in photos. When blue and red overlap, they can create pink or dark red fringes near the base of green curtains.
Sometimes, especially during weaker displays, auroras may appear white or gray to the naked eye. This isn’t a different color emission — it’s due to the eye’s limited ability to distinguish color in low light [5]. Long-exposure cameras, however, can capture the full spectrum even when our vision cannot.
In Iceland, you’re most likely to see green on any clear winter night with moderate auroral activity, and if you're lucky you'll spot purple and pink hues too.
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What Forms Do the Lights in Iceland Take?
The auroras can take different forms — Arcs, Curtains, Spirals and Swirls, and Coronas — which are affected by the movement of charged particles within Earth’s magnetosphere and how they interact with the upper atmosphere. On your visit to Iceland you're most likely to see the forms of arcs and curtains (in the color green).
Most commonly, the aurora appears as an arc — a long, horizontal band of light stretched across the sky. These arcs are formed along magnetic field lines, which funnel solar-charged particles toward the polar regions. Arcs are typically the first structure you’ll see during an auroral display and are relatively stable, serving as the starting point for more dynamic shapes. Their calm appearance is due to lower levels of geomagnetic activity and more uniform electron precipitation.
As geomagnetic activity increases, those arcs often evolve into what are called curtains. These ripple like fabric caught in the wind, hanging vertically and fluttering as energetic particles collide with atmospheric gases. The curtain-like appearance results from variations in the intensity of particle precipitation along different magnetic field lines. Bright folds in the curtain are due to areas where more particles are striking the atmosphere, while dimmer regions show lower activity. The vertical dimension of these curtains can span altitudes from roughly 80 to 300 kilometers, depending on the energy of the particles involved.
In more turbulent auroral events, the sky can break into spirals and swirls. These patterns emerge when the incoming particles begin to twist along the field lines or when irregularities in the magnetospheric electric fields cause the aurora to fragment. Swirling structures are highly dynamic and unpredictable—often forming rapidly, changing shape within seconds, and then dissipating entirely. These are the hallmarks of strong geomagnetic disturbances, often tied to coronal mass ejections or solar wind bursts that compress and destabilize Earth’s magnetosphere.
Perhaps the most dramatic auroral form is the corona. This occurs when the aurora appears to burst outward from a single point directly overhead, giving the illusion that the light is radiating in all directions. Scientifically, this is the result of perspective. When you are positioned directly beneath a very active display, you’re looking straight up into the center of a highly energized auroral arc. From that vantage point, the aurora seems to explode outward like spokes on a wheel. The physics behind it remains the same—charged solar particles exciting atmospheric gases—but the geometry between the observer and the incoming field-aligned currents creates this dramatic effect.
What causes the changing forms of Auroras?
In short, this dynamic behavior is driven by:
- Variations in the solar wind’s strength and magnetic field orientation
- Geomagnetic storms caused by CMEs
- Resonances in the magnetosphere’s field lines, known as field-aligned currents
These field-aligned currents are sometimes referred to as Birkeland currents, named after Norwegian physicist Kristian Birkeland, who was among the first to link auroras to solar particles [6].
The forms the aurora takes are not random — they reflect the underlying physics of how solar wind energy is transferred into Earth’s magnetic field and then down into the atmosphere. Variations in the strength and direction of the solar wind, changes in the interplanetary magnetic field, and local ionospheric conditions all play a role in shaping the light show. Magnetospheric substorms, which occur when energy stored in Earth’s magnetic tail is suddenly released, often serve as the trigger for rapid auroral restructuring.
In Iceland, thanks to its location under the auroral oval, these forms are often visible on a single night, sometimes in sequence, although most seen forms are arcs and curtains. Each display is shaped by real-time space weather conditions, which is why no two auroral shows are ever the same.
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Do the Northern Lights Make a Sound?
I know it sounds made up. But actually… maybe not?
For years, scientists believed auroras were completely silent. But some anecdotal reports people have heard faint crackles, hisses, or pops during particularly strong displays. The indigenous Sami people of Finland, Sweden and Norway tell of myths mentioning noises when the aurora occurs and even workers posted in these high altitudes have reported hearing odd sounds when the aurora appears. But until now no scientific research has backed this up.
Recent studies out of Finland, by Professor Emeritus Unto K. Laine at Alto University, suggest that the phenomenon is more common than previously though. Simultaniously the study cancels the argument that the aurora borealis needs to be exceptionally bright and lively, even suggesting they don't need to be visible at all [7]. So while you hunt for the aurora in Iceland you might hear faint crackling sounds that may just be the auroras whispering to you.
Does Moonlight Affect the Northern Lights?
Moonlight doesn’t stop the aurora from appearing, but it can dim your view, especially if the display is faint. A full moon can wash out weaker lights, much like light pollution from cities does. That said, strong auroras can still shine through bright moonlight, and I’ve seen stunning green arcs even with a full moon overhead (it just adds a little “mystic drama” to your photos, if you ask me).
If you’re planning a northern lights hunt, try to aim for a new moon or a night with less lunar brightness if you want the clearest views.
Experience the Aurora Borealis with Travel Reykjavík
If you’re dreaming of standing under Iceland’s glowing skies while the northern lights dance overhead, let Travel Reykjavík turn that dream into reality. As a proudly family-owned company with over 80 years of experience (yes, we’ve been at it since 1945!), we know these landscapes — and these lights — better than most.
We tailor to all travelers' needs with cozy group tours, custom-tailored private outings, epic multi-day winter adventures, and thrilling super jeep excursion that gets you far off the beaten path.
Our aurora tours are all designed with one mission in mind: helping you witness the magic of the aurora borealis in the best possible way.
We’re here to guide you through one of the most unforgettable experiences on Earth.
Book Your 5-Day Northern Lights Hunt Today!
Sources
1. Royal Belgian Institute for Space Aeronomy. (n.d.). Solar wind: stream of charged particles escaping the Sun. Retrieved from https://www.aeronomie.be/en/encyclopedia/solar-wind-stream-charged-particles-escaping-sun
2. Geophysical Institute, University of Alaska Fairbanks. (n.d.). Aurora forecast. Retrieved from https://www.gi.alaska.edu/monitors/aurora-forecast
3. Canadian Space Agency. (n.d.). The colours of the northern lights. Retrieved from https://www.asc-csa.gc.ca/eng/astronomy/northern-lights/colours-of-northern-lights.asp
4. Royal Belgian Institute for Space Aeronomy. (n.d.). Multi-wavelength observations and modelling of aurora. Retrieved from https://www.aeronomie.be/en/annual-report/multi-wavelength-observations-and-modelling-aurora
5. NOAA Space Weather Prediction Center. (n.d.). Aurora tutorial. Retrieved from https://www.swpc.noaa.gov/content/aurora-tutorial
6. NASA Goddard Space Flight Center. (n.d.). Auroral poster. Retrieved from https://pwg.gsfc.nasa.gov/polar/EPO/auroral_poster/aurora_all.pdf
7. Laine, E. P., & Hao, Y. (2022). Sound producing mechanism in the temperature inversion layer and its sensitivity to geomagnetic activity. ResearchGate. Retrieved from https://www.researchgate.net/publication/359861885