Solar Wind and Bz — Predicting Geomagnetic Storms

Solar Wind and Bz — Predicting Geomagnetic StormsHow DSCOVR/ACE solar-wind monitors at L1 give 30–90 min warning of geomagnetic storms. Speed, density, Bz, Bt — the "storm imminent" recipe operators watch.Solar wind is the continuous stream of charged particles flowing from the sun. Speed, density, and embedded magnetic field direction determine whether a CME or coronal hole stream sparks a geomagnetic storm.The numbers

Speed (km/s): Quiet ~350. Coronal-hole streams 500-700. CME-driven 800-2000+.

Density (p/cc): Quiet ~5. CME sheath spikes to 30+.

Bz (nT): N-S component of embedded field. Negative (southward) = bad. Persistent Bz <= -10 nT = storm imminent.

Bt (nT): Total field strength.

Storm imminent recipe1. Solar wind >= 500 km/s 2. Bz negative <= -10 nT 3. Sustained for hoursDSCOVR and ACE at L1 give 30-90 min warning.Part of the BloomWX learn library — beginner-friendly explainers covering every surface of the BloomWX weather dashboard. Open BloomWX to see live data for any U.S. county.