When you hear that a 'geomagnetic storm' is coming, that's aurora hunters' best news. A storm can push bright Northern Lights far brighter and even further south than usual.
Here's what a geomagnetic storm actually is.
What triggers a storm
Two things: coronal mass ejections (CMEs) — huge blobs of solar plasma flung out during solar flares — and coronal holes that release fast solar wind. When either hits Earth's magnetic field, it disturbs it: a geomagnetic storm.
The G and KP scales
Storms are rated G1 (minor) to G5 (extreme), matching KP 5 to KP 9. In Ruka you don't need a storm at all — KP 1–2 already shows aurora — but a G2+ storm turns a good night into an unforgettable one.
What a storm looks like from Ruka
During a strong storm the aurora fills the sky overhead, dances quickly and often shows reds and purples. On rare extreme storms the lights are visible far to the south, but under Ruka's oval they're simply spectacular.
Catching a storm
Storms are usually flagged 1–3 days ahead. If you're already here on several nights with the flexibility to chase clear skies — as on our aurora tours — you're perfectly placed to catch one.