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Dancing across Iceland’s night sky, the northern lights are a dazzling result of solar wind and charged particles colliding with atoms and molecules high above Earth. To uncover the science behind this natural wonder, we spoke with Icelandic astronomer Sævar Helgi from icelandatnight.is. Read on to discover why Hotel Rangá in south Iceland is one of the best places in the world to experience and photograph the northern lights.
What are the northern lights, and what conditions are necessary for them to appear in the night sky?
The northern lights are simply the result of energetic solar particles ionizing oxygen and nitrogen in Earth’s upper atmosphere. When these atoms and molecules get ionized or excited, they give away light: the northern lights. This happens due to the interaction of solar particles, which are magnetic, and Earth’s magnetic field. When our magnetic field interacts with the solar particles, energy is transported down towards the polar regions, and the aurora appears in our skies.
For beautiful lights to be seen, conditions have to be favorable. By that, I mean both solar wind and local cloud cover. We need clear or partly clear skies, as well as a solar wind with negative polarity, called Bz. When the solar wind has a negative Bz (points south), it links up with Earth’s magnetic field and beautiful magic happens. This can happen in the auroral oval even if activity is low, especially in the months closest to the equinoxes.
That’s why aurora chasers should focus on watching the Bz value instead of the Kp-index. You can watch the Bz value at icelandatnight.is.
To summarize, we need dark, clear or partly clear skies and favorable solar wind to see the Northern Lights.
Is it possible to predict when the northern lights will appear?
Yes! But there is a caveat. By watching the Bz value and how our local magnetic field is behaving, it is possible to predict when auroras will appear with amazing accuracy. The caveat is that you can only do that accurately within an hour or so. This is because these predictions are based on satellites 1.5 million km away from Earth that are being bombarded by solar wind. You can see these observations displayed under real time space weather data at icelandatnight.is.
The most common time for the Northern Lights to appear in the sky is around 23 (11 pm) in the evening. So if the night is quiet and people ask, when will the Northern Lights appear, I always say, I’ll switch them on around 11 o’clock. If conditions are favorable and you keep an eye on the sky from 22:30 to 01:00, you are quite likely to see something.
We can also have a decent idea of how active the aurora will be for the next few days or weeks even by monitoring solar activity. We’ve learned that auroras repeat every 27 days or so due to what’s called coronal holes that eject high speed solar wind into space.
Then we also know that auroras are more likely to appear close to the equinoxes. You can read more about the best time to see the northern lights in Iceland here.
What role does the solar wind play in creating auroral displays here in Iceland?
The solar wind plays the biggest role in creating auroral displays. That is because the solar wind is what causes the northern lights. If there’s hardly any solar wind blowing around Earth, little or no aurora can be seen in the sky. That’s why we monitor the speed of the solar wind and its embedded magnetic field very closely. It’s the key to successful aurora chasing.
Can you explain how solar flares and coronal mass ejections from the Sun influence the intensity and frequency of the northern lights?
Solar flares are sudden bursts of energetic light from active regions on the Sun. Sometimes they are followed by coronal mass ejections (CMEs). CMEs are clouds of plasma or energetic solar particles hurled into space at incredible speeds. However, CMEs have to be directed towards Earth to cause the northern lights. If Earth’s embedded magnetic field is south-facing, then CMEs can lead to some epic auroras.
Earth-directed CMEs happen infrequently. However, when they do happen, these CMEs can cause powerful solar storms. As a result, we are able to see the most impressive and colorful aurora displays, such as the one that happened on October 10 2024.
CMEs are most common around the solar maximum, which is the peak of the 11 year activity cycle of the Sun. In fact, some of the best CMEs have happened in the descending part of the solar maximum cycle. This is currently the stage we are experiencing, which is why we are quite optimistic and hopeful for the coming years. After that, coronal holes will become more frequent and stable which will lead to more common aurora shows. So the best aurora years are actually ahead.
How does the solar cycle affect aurora visibility in Iceland?
We are lucky enough to live under the auroral oval. That means that auroras appear in our sky every night. However, their appearance to the naked eye is dependent upon the weather and solar activity.
In the years close to the peak of the solar cycle, we generally see less auroras than in the two or three years after. This is because Earth directed CMEs aren’t very common. What’s more, coronal holes are even less common. However, when the Sun’s activity starts to decline, coronal holes become more numerous and more stable. As a result, the chance of seeing the northern lights becomes more and more common.
I know it sounds counterintuitive, but this really is what decades of data has taught us. Then, in the years around solar minimum, powerful aurora storms are less common. However, the aurora is still always there.
Why do we see different aurora colors—like green, red and pink auroras?
Different aurora colors occur when atoms and molecules of oxygen and nitrogen at various altitudes in Earth’s upper atmosphere become excited. The most common silvery-green glow comes from oxygen around 100 km above the surface. At higher altitudes—up to 400 km—oxygen can also produce a deep red hue, while nitrogen at roughly 90 km creates shades of violet. Pink auroras, meanwhile, are a mix of emissions from both oxygen and nitrogen.
The intensity and variety of colors depend on the energy and density of the solar wind. During powerful solar storms, the aurora can appear especially vibrant, and red light may even be visible to the naked eye.
To unaided eyes, faint auroras often look greyish, since human night vision struggles to detect color in dim light. But during bright auroral substorms, when the lights intensify, their true greens, reds, violets, and pinks become clearly visible.
What is geomagnetic activity, and why does Iceland’s location near the magnetic poles make it such a prime viewing spot?
Geomagnetic activity occurs because Earth’s magnetic field extends into space like a protective bubble. When charged particles from the Sun—known as the solar wind—strike this field, it shakes and shifts, much like laundry on a line in the wind. This interaction increases geomagnetic activity, which scientists measure on a scale from zero to nine called the Kp-index. The Kp-index doesn’t indicate how bright or colorful the aurora will appear, but rather the strength of geomagnetic disturbances. For aurora chasers, it’s important to know that breathtaking northern lights can still appear even when the Kp-index is low.
Iceland is one of the best places in the world to witness the aurora borealis because of its location near Earth’s magnetic pole. In space, solar particles are guided along magnetic field lines toward the poles, colliding with the atmosphere at altitudes of about 80 km and above. This creates an oval-shaped auroral zone around each pole—a zone that Iceland sits directly beneath. That’s why the northern lights are visible here on nearly every clear, dark night.
What tips do you recommend for photographing the northern lights, especially for Hotel Rangá guests who may be seeing them for the first time?
First, dress warmly. Second, be patient—capturing the aurora often requires waiting for the lights to appear. Plan to stay outside for at least an hour or two so you don’t miss auroral substorms, when the lights become brightest, most dynamic, and most beautiful.
If you’re photographing, I recommend using the Rangá observatory as shelter, since it can get quite windy. Make sure your batteries are charged, and don’t forget to look up! The aurora is best enjoyed with your own eyes, not just through a camera screen.
These days, photographing the northern lights with a smartphone is surprisingly easy. Simply point your phone at the sky, hold it steady for about three seconds, and shoot. With a little practice, you’ll get great results.
Do you ever encounter any misconceptions about the northern lights?
Yes, absolutely. One of the most common misconceptions is putting too much emphasis on the Kp-index. Many people think it predicts the aurora, but it doesn’t. In fact, it’s practically useless in Iceland because we are already within the auroral oval. Another frequent misunderstanding is the oval model shown in many apps—it doesn’t indicate where the aurora is visible at a given moment.
There’s also the belief that the aurora is always grey. In reality, they only appear grey to the human eye when they’re quiet. Once the aurora brightens, the colors emerge—and they can be absolutely stunning.
Why do you think Hotel Rangá is such a great place to see the northern lights?
Rangá is ideally located in a dark rural area—the perfect setting for aurora viewing. The hotel even switches off the parking lot lights to reduce light pollution and provide an even better view.
Hotel Rangá also features the Rangá observatory, where guests can observe the stars, the Moon, and the planets while waiting for the northern lights. And of course, the staff keep watch and let guests know as soon as the aurora appears with their excellent aurora wake-up call service.
Where Science Meets Wonder
Thanks to the insights of Sævar Helgi, we’re reminded that the northern lights are more than just a beautiful spectacle—they are living proof of the powerful connection between the Sun and Earth. From solar flares and geomagnetic activity to the way atoms and molecules in our atmosphere release vibrant colors, every aurora tells a story written across the night sky. And while the science is fascinating, nothing compares to experiencing the aurora borealis in person.
At Hotel Rangá, with its dark skies and stunning South Iceland setting, guests have a front-row seat to one of nature’s greatest shows. Whether you come to capture the lights on camera or simply watch them dance overhead, the northern lights promise an unforgettable memory that will stay with you long after the glow fades.
Ready to witness the Northern Lights for yourself? Book your stay at Hotel Rangá and experience Iceland’s most spectacular natural wonder right outside your door.
