From Sun to Earth
Solar flare: Radiation reaches Earth in ~8 minutes; can cause ionospheric effects quickly. CME: Ejected 1–3 days before impact; travel time depends on speed (often 400–800 km/s, fast CMEs over 1000 km/s). Arrival: When the CME (or its shock) hits the magnetosphere, Kp rises, often over hours. Main phase: Storm can last hours to days; recovery follows as the CME passes.
Forecasting
NOAA SWPC and others use solar images and solar wind data to forecast CME arrival (with uncertainty of several hours). Kp and aurora forecasts are updated as the event approaches. Cosmic Radar shows the daily Kp and reported flares/CMEs so you can see the timeline of events.
Sources and further reading
- NOAA – CME arrival – Forecast discussion and CME timeline
- NASA DONKI – CME and space weather event list
- ACE Solar Wind – Real-time solar wind