The serene, dancing lights of the Aurora Borealis seem a world away from the violent, fiery surface of the Sun. Yet, these two phenomena are directly connected in a cosmic cause-and-effect relationship that spans 93 million miles of space. The story of the Northern Lights doesn’t begin in our atmosphere, but with powerful explosions on our home star.

Understanding the Northern Lights requires looking at two key solar events: solar flares and their powerful cousins, Coronal Mass Ejections (CMEs). This guide will break down what each phenomenon is and how they work together to create Earth’s most spectacular natural light show.

To understand the aurora, we first need to understand the Sun’s dynamic and sometimes explosive behavior. The Sun constantly sends out a stream of particles, but certain events can turn this gentle stream into a powerful storm.

What is a Solar Flare?

A solar flare is a tremendous explosion on the surface of the Sun, occurring when magnetic energy that has built up in the solar atmosphere is suddenly released. This event releases a massive burst of radiation, which travels at the speed of light. This means the light and energy from a solar flare reach Earth in just over eight minutes. While flares are incredibly powerful, they are not the main cause of the aurora. Think of a flare as the ‘muzzle flash’ of a cannon—an incredibly bright and intense burst of light and energy that signals an event has happened. It’s what comes next that truly powers the Northern Lights.

What is a Coronal Mass Ejection (CME)?

Often accompanying a solar flare is a Coronal Mass Ejection (CME). If the flare is the cannon’s flash, the CME is the ‘cannonball’. A CME is a massive cloud of plasma and magnetic field that is hurled from the Sun’s corona into space. This cloud of charged particles travels much slower than a flare’s radiation, taking anywhere from 1 to 3 days to cross the vast distance to Earth. It is this enormous, energetic cloud of solar material that, when aimed at Earth, dramatically interacts with our planet’s magnetic field and is the primary driver behind strong, widespread, and vibrant auroral displays.

The Solar Wind: A Constant Flow

Even when there are no flares or CMEs, the Sun constantly emits a stream of charged particles called the solar wind. This wind flows outward in all directions at speeds of around one million miles per hour. The solar wind is responsible for the ‘everyday’ auroras that occur regularly in the polar regions, often visible only from high-latitude locations like northern Scandinavia, Alaska, and Canada. A CME is essentially a massive, fast-moving, and dense wave within this solar wind, capable of overpowering Earth’s defenses and creating a geomagnetic storm that lights up the sky.

The journey of particles from the Sun to our atmosphere is a multi-step process, culminating in the beautiful lights we see. Earth’s own magnetic field plays the crucial role of both protector and guide.

The Collision with Earth’s Magnetosphere

When a CME or a fast solar wind stream reaches Earth, it first collides with our planet’s protective magnetic shield, the magnetosphere. This invisible field, generated by Earth’s molten core, deflects the vast majority of harmful solar particles. However, a powerful CME can compress and rattle this shield, transferring huge amounts of energy into it. The magnetosphere channels this influx of energetic particles along its magnetic field lines, directing them down towards the weakest points in the shield: the North and South magnetic poles.

Creating the Aurora’s Glow

The grand finale occurs in Earth’s upper atmosphere, at altitudes of 60 to over 200 miles (100-320 km). As the captured solar particles are funneled towards the poles, they slam into atoms of oxygen and nitrogen. These collisions ‘excite’ the atmospheric atoms, giving them a temporary boost of energy. To return to their normal state, the atoms must release this excess energy in the form of light particles called photons. Billions upon billions of these collisions create the shimmering, dancing curtains of light we know as the aurora. The intensity of the solar event directly impacts the brightness and extent of the display.

• Solar flares are bursts of radiation (light) that reach Earth in 8 minutes.
• Coronal Mass Ejections (CMEs) are clouds of particles that are the primary cause of strong auroras, taking 1-3 days to reach Earth.
• The Northern Lights are caused by these solar particles colliding with oxygen and nitrogen in our upper atmosphere.
• Earth’s magnetic field (the magnetosphere) protects us and funnels these particles toward the poles.
• A stronger solar event, like a large CME, leads to a more intense and widespread aurora, sometimes visible at much lower latitudes.
• The Sun operates on an ~11-year cycle of activity, with a ‘solar maximum’ period featuring more frequent flares and CMEs.
• The everyday, faint aurora is caused by the Sun’s constant ‘solar wind’.

Q: Does every solar flare cause Northern Lights? A: No. A solar flare itself doesn’t cause the aurora. It’s the associated CME that does, and the CME must be aimed towards Earth to have an effect. Many flares and CMEs are directed away from our planet.

Q: Are solar flares and CMEs dangerous to people on Earth? A: No, people on the ground are protected by the magnetosphere and atmosphere. However, very strong geomagnetic storms can disrupt satellites, radio communications, and power grids. Astronauts in space are more exposed.

Q: What is the ‘solar cycle’? A: The solar cycle is the Sun’s approximately 11-year cycle of magnetic activity. It goes from a quiet period (solar minimum) to a very active period (solar maximum), where flares and CMEs are much more common, resulting in more frequent auroras.

• NASA – What Is a Solar Flare?
• NOAA Space Weather Prediction Center – Coronal Mass Ejections (CME)
• Space.com – Solar Flares: What Are They & How Do They Affect Earth?

Professional aurora photography isn’t just about camera settings; it’s about Atmospheric Physics.

Your settings must change based on the speed of the solar wind and the clarity of the air.

• Fast Aurora: Needs fast shutter (2-5s) or it blurs.
• High Humidity: Needs lens heaters or careful checking for fog.
• High Clouds: Diffuse the stars, requiring sharper focus checks.

Below is the Aurora Photographer’s Cockpit. It pulls live data from 4 separate weather and space APIs to calculate the exact constraints you are shooting under right now.

1. Aurora Speed vs. Shutter Speed

Our cockpit analyzes the Solar Wind Speed (km/s). If this number is high (>600 km/s), the aurora curtains are moving rapidly. If you use a standard 15-second exposure, those beautiful curtains will turn into a green smear. The cockpit calculates the “Max Shutter” to freeze that motion.

2. The Dew Point Spread (Lens Safety)

Look at the “Lens Safety” metric above. This calculates the difference between the Air Temperature and the Dew Point. If this number is small (<2°C), moisture will condense on your cold front lens element within minutes. Pro Tip: If the alert is flashing, keep hand warmers attached to your lens barrel.

3. Magnetic Power (Bz)

The “Bz” value tells us the brightness intensity. A negative number means bright aurora. If the number is positive (North), the aurora will be faint. The cockpit adjusts the recommended ISO automatically: High ISO (3200+) for faint aurora, Low ISO (800-1600) for bright storms to reduce noise.

If you are only looking at the Kp Index, you are looking at old data. To know exactly how strong the aurora is right now, you need to look at the magnetic field data coming from satellites 1 million miles away.

Specifically, we look at the Bz (Interplanetary Magnetic Field). Think of this as a “Magnetic Door.”

• Bz is Negative (South): The door is OPEN. Solar wind pours in. Aurora is strong.
• Bz is Positive (North): The door is LOCKED. Solar wind bounces off. Aurora is weak.

Below is our Pro-Level Magnetic Dashboard showing the live status of this door.

1. The Bz (Direction) – The Most Important Number

This is the “Latch” on the door.
– If you see a Negative Number (e.g., -10 nT), get your camera ready. The further negative it goes, the stronger the storm.
– If you see a Positive Number (e.g., +10 nT), the aurora will likely fade away, even if the Kp index is high.

2. The Bt (Strength)

This is how hard the wind is pushing on the door. A high Bt (over 15 nT) combined with a negative Bz creates the most violent and colorful displays.

3. Speed & Density

This is the fuel. High speed (>500 km/s) creates purple/pink colors. High density (>10 p/cm³) creates brightness.

Q: Can the Bz change quickly?
A: Yes. It can flip from North to South in seconds. This is why the aurora often “dances” or explodes suddenly, then fades away just as fast.

Q: What is a “Substorm”?
A: When the Bz stays South (Negative) for a long time, energy builds up in Earth’s magnetic tail. Eventually, it snaps back like a rubber band, releasing massive energy. This is a substorm, and it creates the brightest, fastest-moving auroras.

Most people expect the Northern Lights to be green. And usually, they are. But during intense solar storms, the sky can explode into shades of pink, purple, red, and even blue.

The colors you see depend on two invisible factors happening in space right now:
1. Which gas is being hit (Oxygen or Nitrogen).
2. How hard it is being hit (Solar Wind Speed).

Below is our Live Aurora Palette, which analyzes real-time satellite data to predict which colors are physically possible in the sky at this exact moment.

💚 Green (The Most Common)

Cause: Low-altitude Oxygen (60-150 miles up).
Why: Our eyes are most sensitive to green light, and oxygen is abundant at this altitude. When the solar wind hits these atoms, they emit a specific wavelength of green light (557.7 nm).

💜 Purple & Pink (The Fast Movers)

Cause: Nitrogen (below 60 miles).
Why: To get this low in the atmosphere, the solar wind particles need to be moving very fast (usually over 600 km/s). They “punch” through the oxygen layer and hit the nitrogen below, causing it to glow pink or purple. This is often seen at the very bottom of aurora curtains.

❤️ Red (The Rare Beauty)

Cause: High-altitude Oxygen (above 150 miles).
Why: At very high altitudes, oxygen is less dense. It takes a long time for these atoms to emit red light. If the solar wind is too dense or active, it interrupts this process. Therefore, pure red auroras are rare and usually only seen during massive geomagnetic storms.

Q: Why do cameras see more color than my eyes?
A: Human eyes are not good at seeing color in the dark (our “cones” shut down). Cameras use long exposures to collect light over several seconds, revealing the true vibrant colors that our eyes perceive as faint grey or white.

Q: What is the rarest color?
A: Blue. It requires nitrogen to be hit at very high energies during extremely violent solar storms. It is almost never seen by the naked eye.

Knowing exactly what time to go outside is the difference between freezing in the cold for hours or seeing the show of a lifetime.

Unlike a standard weather forecast, seeing the aurora requires a “Triple Lock” of conditions:
1. Darkness: It must be post-sunset (nautical twilight).
2. Activity: The Kp index must be high enough.
3. Clarity: Cloud cover must be low.

Below is our real-time Hourly Aurora Forecast for tonight, which automatically processes these three factors to give you the best viewing window.

The “Magnetic Midnight” Rule

Scientifically, the aurora is most active during “Magnetic Midnight.” This is not 12:00 AM on your clock. In Iceland and much of Northern Europe, Magnetic Midnight usually occurs between 22:00 (10 PM) and 01:00 (1 AM). This is when the Earth’s magnetic field lines are best aligned to funnel solar particles into the atmosphere.

Why Early Morning can be Good

If a “substorm” occurs, the aurora can explode into color at any time of darkness. We often see massive displays at 3:00 AM or 4:00 AM when most people have gone to sleep. Check the graph above—if you see green bars in the early morning hours, set an alarm!

Q: Can I see them as soon as the sun sets?
A: Usually, no. You need “True Darkness.” Even if the sun sets at 5 PM, you might need to wait until 6:30 PM for the sky to be dark enough for the aurora colors to pop.

Q: Does the timeline update?
A: Yes, this page updates every hour with the latest data from NOAA satellites and local weather stations.