Welcome to our Aurora Forecast Glossary, aka your guide to what the h*ck we’re talking about when it comes to the Northern Lights. We get it—words like “solar wind” and “Kp index” can sound a bit like space gibberish. But don’t worry, we’ve broken it all down into plain, simple explanations that anyone can understand.
By the end of this, you’ll know exactly what to look for in an aurora forecast and why those magical lights appear in the sky. Whether you’re chasing the Aurora Borealis for the first time or just want to sound smart about space weather, this guide has got you covered. Let’s get started!
A
- Aurora Borealis (Northern Lights): Colorful lights in the sky near the North Pole caused by particles from the Sun colliding with gases in Earth’s atmosphere. The color depends on the type of gas: oxygen produces green or red, while nitrogen creates purple or blue.
- Auroral Arc: A common aurora shape, appearing as a curved or wavy stripe of light stretching across the sky.
- Auroral Oval – A ring-shaped area around the magnetic poles where auroras are most likely to appear. During geomagnetic storms, the oval expands, allowing auroras to be seen farther south.
- Auroral Substorm
A sudden burst of auroral activity, making the lights brighter and more dynamic. It’s caused by energy released in Earth’s magnetosphere.
B
- Bz (Southward Magnetic Field)
A measure of how well the Sun’s magnetic field aligns with Earth’s. A negative Bz means Earth’s “door” is open to solar energy, increasing aurora chances. - Bow Shock
The point where the solar wind slows down and compresses as it hits Earth’s magnetic field.
C
- CME (Coronal Mass Ejection)
A huge eruption of plasma and magnetic energy from the Sun’s surface. CMEs are a primary cause of strong auroras. If a CME is Earth-directed, auroras may occur 1–3 days later. - Clear Skies
Essential for seeing the aurora. Clouds can completely block your view, even during strong activity. - Color Variations
- Green: Most common, caused by oxygen at ~100 km altitude.
- Red: Rare, caused by oxygen at higher altitudes (~300 km).
- Purple/Blue: From nitrogen, seen during stronger storms.
D
- Dst Index (Disturbance Storm-Time Index)
Measures how disturbed Earth’s magnetic field is. Lower values (e.g., -50 nT or lower) indicate better chances for auroras. - Diffuse Aurora
A faint, widespread glow in the sky, less structured than bright auroral arcs.
E
- Electron Precipitation Electrons from space enter Earth’s atmosphere and collide with gases, causing them to glow and create auroras.
- Equinox Effect
Auroras are more frequent during the spring (March) and fall (September) equinoxes because Earth’s position aligns better with the solar wind.
F
- Forecast Map
A live map showing where auroras are likely visible. It displays the auroral oval and updates in real time. - Flux
Measures how much solar energy is hitting Earth. Higher flux values mean more energy for auroras.
G
- Geomagnetic Latitude
Your position relative to Earth’s magnetic poles. Higher geomagnetic latitudes are better for aurora viewing. - Geomagnetic Storm
A disturbance in Earth’s magnetic field caused by solar wind or CMEs. The stronger the storm, the farther south auroras are visible. - G-Scale (Geomagnetic Storm Scale)
A rating system for geomagnetic storms:- G1: Weak auroras near the poles.
- G5: Extreme storms with auroras visible far south.
I
- IMF (Interplanetary Magnetic Field)
The Sun’s magnetic field, carried by the solar wind. A strong IMF combined with a southward Bz creates strong auroras.
K
- Kp Index
A 0–9 scale measuring geomagnetic activity:- 0–2: Weak auroras near the poles.
- 3–4: Moderate auroras in northern regions like Canada or Scandinavia.
- 5+: Strong auroras visible farther south, like the northern U.S. or central Europe.
- Kilometers per Second (km/s)
The speed of the solar wind. Faster solar wind (above 400 km/s) increases auroral activity.
L
- Light Pollution
Artificial lights from cities make it harder to see auroras. Always head to a dark area for the best view.
M
- Magnetosphere
Earth’s magnetic shield that protects us from the solar wind. When disturbed, it creates auroras. - Magnetotail
The part of Earth’s magnetic field stretched out on the night side. Energy stored here triggers auroras during substorms.
N
- Negative Bz
When the Sun’s magnetic field points south, it connects better with Earth’s magnetic field, allowing more energy to create auroras.
O
- Oxygen Emission
The green and red colors in auroras are caused by oxygen molecules being excited by energy.
P
- Plasma
Electrically charged gas from the Sun, which flows as solar wind. Plasma interactions with Earth’s magnetic field create auroras. - Proton Event
A burst of high-energy particles from the Sun that can cause auroras and sometimes disrupt radio signals.
S
- Solar Cycle
The Sun’s activity rises and falls over an 11-year period. More activity means more frequent and stronger auroras. - Solar Flare
A sudden burst of energy from the Sun, often accompanied by X-rays and particles. Flares can cause radio blackouts and auroras when they interact with Earth.
Example: An X-class solar flare can cause auroras within minutes to hours if the conditions are right. - Solar Wind
A continuous stream of charged particles flowing from the Sun. Faster and denser solar wind increases the likelihood of auroras. - Southward Bz
The condition where the Sun’s magnetic field aligns perfectly to allow energy transfer to Earth’s magnetosphere, creating auroras. - Substorm
A sudden “explosion” of auroral activity caused by the release of energy stored in Earth’s magnetotail.
T
- Timeline
Auroras are most active between 10 PM and 2 AM local time, but strong activity can happen at any time.
V
- Van Allen Belts
Zones of trapped radiation around Earth that contribute to auroras during strong geomagnetic activity. - Visibility Forecast
Predictions showing where and when auroras are likely visible, based on the Kp index, weather, and location.
Z
- Zenith
The point directly above you in the sky. During strong auroras, the lights can fill the zenith with vibrant colors.