Glossary
- Aurora Odds
- A provisional estimate of auroral activity reaching a location during a dark hour. Weather is separate and never changes this number.
- Sky conditions
- Cloud cover, darkness and moonlight shown beside the aurora forecast. These describe whether the sky is practical to observe, not whether auroral activity exists.
- Kp
- A global 0 to 9 index of geomagnetic disturbance. Higher Kp pushes visible aurora farther from the poles, but it does not guarantee clear skies or darkness.
- Bz
- The north-south direction of the solar wind magnetic field. Negative Bz opens the door for stronger aurora; positive Bz often suppresses activity.
- Solar wind
- A stream of charged particles from the Sun. Faster, denser solar wind can energize aurora when the magnetic field orientation is favorable.
- Substorm
- A burst of auroral activity that can brighten the sky for tens of minutes. Substorms are local and timing-sensitive, so they are hard to promise hours ahead.
- OVATION
- NOAA’s short-range model of auroral probability around the oval. AuroraOdds uses it server-side and sends only a small raster image to the browser for the map.
- Geomagnetic latitude
- Latitude measured against Earth’s magnetic field rather than the map grid. It explains why places at similar geographic latitude can have very different aurora odds.