What is an Aurora?
Aurora is the glow or light produced when electrons from space flow down Earth’s magnetic field and collide with atoms and molecules in the upper atmosphere. This interaction creates light, similar to how neon lights work.
What are the Northern and Southern Lights?
The aurora is called the Northern Lights (Aurora Borealis) in the northern hemisphere and the Southern Lights (Aurora Australis) in the southern hemisphere. The term ”Aurora” comes from Latin and was first used by Galileo, named after the goddess of dawn. ”Borealis” means ”northern,” while ”Australis” means ”southern.”
What causes the aurora?
Auroras form when the solar wind from the sun interacts with Earth’s magnetic field (magnetosphere). When solar wind speeds up and the interplanetary magnetic field turns southward, geomagnetic activity increases, making auroras brighter and more active.
The image below shows Earth’s magnetic shield (the magnetosphere) and where electrons get supercharged (shown in red). The red area on the right is where the electrons that create nighttime auroras get their energy boost—it’s also the birthplace of geomagnetic storms.
Once energized, these electrons follow Earth’s magnetic field lines toward the north and south magnetic poles.
The image below shows Earth with its magnetic field lines guiding electrons down to the atmosphere. The green shaded ring shows the typical shape of the auroral oval around the magnetic pole. The brighter green shapes? Those are the most common aurora patterns you’ll see—curtains, arcs, and dancing lights.
How does this create light?
When these electrons (traveling at 20,000 km/sec—nearly 1/10th the speed of light) collide with atoms and molecules in Earth’s upper atmosphere, they transfer their energy. This raises the atoms to higher energy states. As they return to normal, they release photons—the light particles we see as aurora.
How is the aurora probability calculated?
The app combines the space weather factors described above—solar wind conditions, magnetic field orientation, and Kp index—with your specific location and local viewing conditions to estimate your likelihood of seeing the aurora tonight. We use the Newell Coupling Function, a physics-based model that quantifies how much energy from the solar wind enters Earth’s magnetosphere. This is adjusted for your distance from the auroral oval and practical factors like cloud cover and daylight. The result is a percentage: higher values mean better viewing conditions. Think of it like a weather forecast—80% means conditions are excellent and you should look up, while 20% means it’s unlikely but not impossible.
What is the Kp index, and why does it matter?
The Kp index measures geomagnetic activity on a scale from 0 to 9. Higher Kp values mean the aurora can be seen further from the poles:
- Kp 0-2: Aurora is dim and confined to the Arctic Circle (northern Scandinavia, Alaska, northern Canada).
- Kp 3-5: More active and brighter, extending to central Scandinavia, Scotland, and southern Canada.
- Kp 6-7: Visible from northern United States, northern UK, and northern Germany.
- Kp 8-9: Major storm—aurora visible from mid-latitudes including central US and southern Europe (rare events).”
What solar events create strong auroras?
Two major solar events can trigger intense auroras:
- Coronal Mass Ejections (CMEs): These are massive bursts of plasma ejected from the sun, traveling at high speeds. When a CME reaches Earth, it can cause strong geomagnetic storms and bright auroras extending far from the poles.
- Coronal Holes: These are regions on the sun where high-speed solar wind streams originate. When these streams reach Earth, they can create moderate geomagnetic storms and auroras, though less intense than those from CMEs.
Where should I go to see the aurora?
The best locations are at high latitudes, typically within or near the Arctic Circle. This includes northern Scandinavia (Sweden, Finland, Norway), Iceland, Alaska, northern Canada, Svalbard, and Greenland.
For optimal viewing, seek dark locations away from city lights with an unobstructed view toward the north (or south in the Southern Hemisphere). Elevated locations offer the best vantage points. Light pollution and the full moon can reduce visibility significantly
When is the best time of night to see the aurora?
The most active period is usually between 10 PM and 2 AM local time. However, as geomagnetic activity increases, the aurora may be visible earlier in the evening and later into the morning.
What are the best seasons to see the aurora?
The best times are around the spring and fall equinoxes (March and September), when geomagnetic storms are most frequent. However, winter months (November through February) offer longer periods of darkness at high latitudes, providing more viewing opportunities. Summer’s extended daylight hours make aurora viewing difficult despite active conditions.
Why does the aurora have different colors?
Different colors appear when electrons collide with different atmospheric gases at varying altitudes:
Green (most common): Oxygen at 100-300 km altitude produces the characteristic pale green glow.
Red: Oxygen at higher altitudes (above 300 km) creates deep red hues, often visible during strong storms.
Purple and blue: Nitrogen molecules produce these colors at lower altitudes (below 100 km).
The specific color depends on which gas is struck and how much energy is transferred during the collision.
The image below shows a typical spectrum of aurora.
