Overview
The most spectacular auroras happen during geomagnetic storms — when a burst of solar material slams into Earth's magnetic field.
What causes them
Solar flares and coronal mass ejections (CMEs) fling charged particles into space. When one reaches Earth, it disturbs the magnetic field, driving intense aurora.
What it looks like
During a storm, the aurora brightens, moves fast, fills the sky and can show reds and violets — sometimes visible far south of the usual zone.
Catching one
Storms are forecast a day or two ahead (with uncertainty). Being in Rovaniemi on a clear storm night is unforgettable. See our forecast guide.