The aurora borealis captures the imagination like almost nothing else in nature. We hear from aurora enthusiasts at every level — first-timers trying to understand what they are looking at, experienced chasers wanting to dial in their timing, and everyone in between. Below are the questions we hear most often, answered as clearly and completely as we can.
What is the aurora borealis?
The aurora borealis, also called the Northern Lights, is a natural light display that occurs in Earth's upper atmosphere near the North Pole. It is caused by electrically charged particles from the Sun colliding with atoms and molecules in our atmosphere. When those atoms absorb the energy from the collision, they release it again as light — producing the glowing curtains, arcs, and ripples we call the aurora. The same phenomenon occurs near the South Pole, where it is known as the aurora australis, or Southern Lights.
What causes the aurora?
The Sun constantly streams charged particles into space in what is called the solar wind. When this wind reaches Earth, our planet's magnetic field deflects most of it, but channels some particles toward the polar regions along magnetic field lines. High in the upper atmosphere — between 60 and 200 miles above the surface — these particles slam into oxygen and nitrogen atoms, exciting them to higher energy states. When those atoms return to their normal state, they release the stored energy as visible light. Oxygen at lower altitudes produces the most common green color; oxygen higher up produces red; nitrogen contributes purples and blues.
What is the Kp index?
The Kp index is a scale from 0 to 9 that measures global geomagnetic activity — essentially how disturbed Earth's magnetic field is at any given time. A Kp of 0 means extremely quiet conditions; a Kp of 9 means a severe geomagnetic storm. The higher the Kp, the farther from the poles the aurora becomes visible. At Kp 5 or above, a geomagnetic storm is officially in progress, and aurora can often be seen across large portions of the northern United States, central Europe, and the southern tip of New Zealand. Solar Ruler uses real-time OVATION data from NOAA to show the current auroral oval on its globe, giving you a visual representation of where activity is concentrated.
What Kp level do I need to see the aurora from my location?
This depends on your latitude. As a rough guide: if you live at 65°N or higher (northern Norway, northern Canada, Alaska, Iceland), aurora can be visible at Kp 2 or even 1 on clear, dark nights. At 60°N (southern Norway, Helsinki, Anchorage), you typically need Kp 3–4. At 55°N (southern Scotland, Moscow, southern Canada), expect to need Kp 4–5. At 50°N (northern France, southern England, the northern US border states), Kp 5–6 is usually required. At 40°N (northern Spain, New York, Denver), you need Kp 7 or higher, which corresponds to a strong geomagnetic storm. Use Solar Ruler's globe to check whether the auroral oval is reaching your latitude in real time.
Can I see the aurora with my naked eye?
Yes, absolutely. The aurora was discovered and observed for thousands of years before photography existed. In fact, the human eye sees the aurora differently than a camera does. Long-exposure photographs reveal colors and details that are real but difficult for our eyes to perceive in real time — especially faint reds and purples that cameras capture easily but our vision struggles with in dim conditions. That said, the green aurora is typically visible to the naked eye whenever it is bright enough. During strong events, vivid greens, pinks, and even reds are unmistakably visible without any equipment at all.
When is the best time of year to see the aurora?
The aurora occurs year-round, but you can only see it when skies are dark — which rules out summer months at high latitudes due to the midnight sun. The traditional aurora season runs from late August through April in the Northern Hemisphere. Many researchers note a slight statistical uptick in strong geomagnetic activity around the spring and autumn equinoxes (March and September), possibly linked to how Earth's magnetic field aligns with the solar wind near those dates. For most visitors, the practical best months are October through February, when nights are longest and temperatures keep skies stable and clear.
What time of night is the aurora most active?
Aurora activity peaks around local magnetic midnight, which is roughly when the Sun is on the opposite side of the Earth from your location — typically between 10 p.m. and 2 a.m. local time. The hours from 10 p.m. to 1 a.m. are statistically the most productive for aurora watching in most high-latitude locations. However, strong geomagnetic storms can produce spectacular displays at any hour. It is worth setting an alarm to check conditions in the early morning hours (3–5 a.m.) as well, since some substorm activity peaks just before dawn.
What is an auroral substorm?
A substorm is a sudden, localized intensification of aurora activity that can happen even during otherwise quiet geomagnetic conditions. During a substorm, the auroral oval brightens dramatically, curtains rapidly develop rays and folds, and the display can shift from a quiet green arc to a rapidly pulsing, full-sky show in a matter of minutes. Substorms typically last between 30 minutes and a couple of hours. They are one of the reasons why patience is so important during an aurora session — conditions can change dramatically and quickly, even when the Kp index is relatively low.
Can the aurora be seen during the day?
No. The aurora is always present in the upper atmosphere whenever geomagnetic activity is elevated, but it cannot be seen in daylight because the sky is far too bright. Just as you cannot see stars during the day, you cannot see the aurora when sunlight is illuminating the atmosphere. This is why aurora viewing requires darkness, and why locations with long polar nights — or a total solar eclipse — provide the best opportunities.
Can the aurora be heard?
This is one of the most debated questions in aurora science. Many people throughout history have reported hearing soft crackling, hissing, or clapping sounds during strong aurora displays, but scientists struggled for years to confirm or explain the phenomenon. Research published in the 2010s provided recordings and a possible mechanism: electrostatic discharges occurring in a thermal inversion layer roughly 70 meters above the ground, triggered by the geomagnetic disturbance above. The sounds are subtle and not guaranteed, but they appear to be real. If you find yourself under a strong display in very quiet conditions, listen carefully.
Why is the aurora green? Can it be other colors?
The most common green color comes from excited oxygen atoms at altitudes of roughly 60–150 miles above the surface. At higher altitudes (above 150 miles), oxygen produces a rarer red aurora. Nitrogen molecules create blue and purple hues, often visible at the lower edges of aurora curtains. Pink or magenta fringes — some of the most striking aurora colors — typically appear when the lower edge of a green curtain meets nitrogen emissions. The colors in real life are genuine, not artificially enhanced, though camera sensors pick them up more easily than the human eye in low-light conditions.
Does the Moon affect aurora viewing?
Yes, significantly. A full moon or near-full moon brightens the sky enough to wash out faint auroras, just as it reduces the number of visible stars. During a strong display (Kp 5+), the aurora can overpower moonlight and remain spectacular. But during moderate or faint activity, moonlight can make the difference between a vivid show and barely noticing the aurora at all. Serious aurora watchers plan trips around the new moon phase to maximize the darkness of their viewing conditions.
What is the difference between the aurora borealis and aurora australis?
Scientifically, they are the same phenomenon — caused by the same process and occurring simultaneously at both magnetic poles. The aurora borealis (Northern Lights) occurs near the North Pole; the aurora australis (Southern Lights) occurs near the South Pole. Because most of the Earth's populated land is in the Northern Hemisphere and the auroral oval in the south is centered over Antarctica, the southern lights are far less frequently observed. The best accessible locations for aurora australis are the southern tip of New Zealand, Tasmania in Australia, southern Patagonia in Argentina, and the sub-Antarctic islands.
How does Solar Ruler help me see the aurora?
Solar Ruler displays the real-time NOAA OVATION aurora model as a glowing green band on an interactive 3D globe. The model shows where the auroral oval is concentrated right now — which latitudes and longitudes are under active aurora. If the green band on the globe is pushing down over your region, that is a strong signal that conditions are favorable and you should get outside to a dark location. Solar Ruler also shows your location (with your permission) as an orange marker, so you can immediately see how close you are to the auroral zone. Because the globe updates with current data, it is most useful in the hours immediately before and during an aurora event.
Do solar flares directly cause the aurora?
Solar flares themselves produce a burst of radiation that travels at the speed of light and reaches Earth in about eight minutes — but this radiation interacts primarily with the upper atmosphere in ways that affect radio communications, not visible aurora. The aurora is caused by the stream of charged particles (plasma) that accompanies a coronal mass ejection (CME), which travels much more slowly — typically one to three days to reach Earth. A solar flare may precede a CME, but the flare itself is not the direct cause of the aurora. When both a strong flare and a CME occur, forecasters watch carefully for the incoming plasma cloud, knowing that a geomagnetic storm — and a potential aurora display — may be one to two days away.