The chain: active region (sunspots) → flare (X-rays, 8 min → radio blackout / R) → protons/SEP (mins–hrs → radiation / S) → CME (plasma cloud, 1–4 days → the geomagnetic storm) → Bz at L1 (final 15–60 min warning) → geomagnetic storm (Kp → G: grid/GPS/aurora).
Three things decide severity: (1) CME speed → energy ∝ speed² (2000 km/s = 1.0× Carrington); (2) direction → Earth-directed halo? direct hit vs glancing; (3) Bz at arrival → sustained southward Bz realizes the potential, northward wastes even a fast CME. Bz is only knowable ~15–60 min ahead — so every pre-arrival forecast (incl. the Kp-Est column above) is provisional.
What's actually dangerous: G4–G5 storms (grid GIC/transformer risk, GPS unreliable, satellite drag/loss) — the Quebec/Gannon/Carrington class. R and S matter for HF radio, GPS precision, satellites and polar aviation but rarely touch ground life. Most events are "watch the sky"; the job is flagging the rare one that isn't, without crying wolf.
Earliest → latest warning: delta-class magnetic regions (days) → Earth-directed CME + Enlil ETA (1–4 days) → flare/proton onset (now) → sustained southward Bz at L1 (15–60 min, decisive). Preconditioning: serial CMEs from one region within ~5 days clear the path so the next hits harder — the 1859/2012 signature.
/var/lib/jarvis/knowledge/solar/ — INDEX · data-sources · interpretation · severity-ground-truth · reference-events · early-warning-signals.