Aurora & Space Weather Glossary
Every term you'll meet in aurora forecasting and science, defined in plain language.
A
Airglow
A faint natural glow of the night sky produced by chemical reactions in the upper atmosphere — present even without auroras.
Aurora Australis
The Southern Lights — the Southern Hemisphere's mirror twin of the aurora borealis.
Aurora Borealis
The Northern Lights — glowing light in the northern night sky produced when solar particles make the upper atmosphere emit light.
Auroral Arc
The classic ribbon of aurora — a smooth, elongated band stretching east–west across the sky.
Auroral Corona
The crown-like burst of rays that appears directly overhead when an auroral curtain passes the zenith.
Auroral Oval
The ring-shaped zone around each magnetic pole where auroras occur most often.
Auroral Zone
The band of latitudes where auroras are statistically most frequent — the auroral oval's average footprint.
B
C
Carrington Event
The most extreme geomagnetic storm on record (September 1859), with auroras reported near the tropics.
Corona (Solar)
The Sun's outer atmosphere — a halo of million-degree plasma and the birthplace of the solar wind.
Coronal Hole
A dark region of the corona where the Sun's magnetic field opens into space, releasing fast solar wind.
Coronal Mass Ejection (CME)
A huge eruption of magnetized plasma blasted from the Sun into space — the main driver of strong auroras.
D
G
G-Scale (Geomagnetic Storm Scale)
NOAA's public 1-to-5 rating of geomagnetic storms, from G1 (minor) to G5 (extreme).
Geomagnetic Pole
The point where Earth's idealized magnetic dipole axis meets the surface — the center the auroral ovals ring around.
Geomagnetic Storm
A major disturbance of Earth's magnetic field caused by solar wind structures, rated G1 (minor) to G5 (extreme).
Green Line (557.7 nm)
The specific green wavelength emitted by atomic oxygen — the aurora's signature color.
H
I
IMF Bt
The total strength of the interplanetary magnetic field, regardless of direction.
IMF Bz
The north–south component of the solar wind's magnetic field — the single most important real-time aurora number.
Interplanetary Magnetic Field (IMF)
The Sun's magnetic field carried through the solar system by the solar wind.
Ionosphere
The electrically charged layer of Earth's upper atmosphere, from about 50 to 400 miles up, where auroras occur.
K
L
M
Magnetic Latitude
Your latitude measured from the magnetic pole rather than the geographic pole — what actually determines your aurora odds.
Magnetic Reconnection
The process where oppositely directed magnetic fields snap and reconnect, converting magnetic energy into particle energy.
Magnetometer
An instrument measuring the strength and direction of magnetic fields — the workhorse of aurora monitoring.
Magnetopause
The boundary surface where Earth's magnetic field meets the solar wind.
Magnetosphere
The protective magnetic bubble around Earth carved out of the solar wind by our planet's magnetic field.
Magnetotail
The long tail of Earth's magnetic field stretching away from the Sun, where storm energy is stored before release.
N
P
Plasma
The fourth state of matter — a gas of charged particles — making up the Sun, solar wind, and aurora environment.
Polar Cap
The region poleward of the auroral oval, threaded by magnetic field lines open to the solar wind.
Pulsating Aurora
Patches of aurora that blink on and off every few seconds, common late at night after big displays.
R
S
Solar Cycle
The Sun's roughly 11-year rhythm of rising and falling magnetic activity.
Solar Energetic Particles (SEPs)
High-energy protons and ions accelerated by flares and CME shocks, arriving at Earth within minutes to hours.
Solar Flare
A sudden, intense burst of radiation from the Sun's surface, usually near sunspots.
Solar Maximum
The peak of the Sun's ~11-year activity cycle, when sunspots, flares, and CMEs are most frequent.
Solar Minimum
The quiet trough of the solar cycle, with few sunspots and few solar eruptions.
Solar Wind
A continuous stream of charged particles flowing outward from the Sun through the solar system.
Solar Wind Density
How many particles the solar wind carries per unit volume, typically 1–10 per cubic centimeter.
Solar Wind Speed
How fast the solar wind is moving past Earth, usually 250–500 miles per second.
STEVE
A narrow mauve-purple ribbon of light that appears equatorward of the main aurora — technically not a classic aurora.
Substorm
A sudden release of stored magnetic energy that makes the aurora erupt, brighten, and dance for minutes to an hour.
Sunspot
A dark, cooler patch on the Sun marking intense magnetic activity — the source regions of flares and CMEs.