Reading the sky. The KP index measures geomagnetic disturbance on a 0–9 scale. At KP 3 the oval hugs the pole; by KP 7 the lights dance over southern Scandinavia; a rare KP 9 pushes them to the horizon across all of Europe. Curtains brighten, accelerate, and reach further south as you drag the index — the way a real substorm eats the whole northern sky in minutes. This scene is illustrative; for real forecasts, trust your national met office, not a beautiful web page.