The Sun
The Sun constantly emits a stream of charged particles — electrons and protons — called the solar wind, traveling at 400–800 km/s. During periods of high solar activity, the Sun also produces solar flares and Coronal Mass Ejections (CMEs).
Earth's Magnetic Field
Earth's magnetosphere acts as a protective bubble, deflecting most solar wind particles around the planet. However, at the polar cusps, magnetic field lines converge and funnel particles inward toward the atmosphere.
The Atmosphere — How Colors Form
When charged particles spiral down the magnetic field lines, they collide with oxygen and nitrogen molecules in the atmosphere. These collisions excite the molecules and emit light — the aurora.
The KP Index Explained
The Planetary K-index (Kp) measures global geomagnetic activity on a scale from 0 to 9. It is derived from magnetometers at 13 stations worldwide and updated every 3 hours.
Aurora Glossary
Bz
The north-south component of the interplanetary magnetic field (IMF). Negative Bz allows solar wind energy to flow into Earth's magnetosphere, triggering aurora.
Solar Wind Speed
The velocity of charged particles streaming from the Sun. Normal is 350-500 km/s. During solar storms it can exceed 800 km/s.
OVATION Model
A model from NOAA that predicts the intensity and location of the auroral oval in real time using solar wind data.