Learn the aurora in 5 minutes

Short, jargon-free pages. Each link below opens a one-screen explainer. We are publishing them in batches — first five go live this week.

• What is the Kp index?
• Solar wind Bz, south is good
• The OVATION oval model, simply
• Why cloud forecasts fail 30% of the time
• Bortle scale in 7 stops
• Astronomical, nautical, civil twilight
• Moon phase vs aurora visibility
• Solar cycles 24 → 25 → 26
• Field glossary