A coronal mass ejection is a billion-tonne eruption of magnetised plasma from the Sun's corona, travelling at hundreds to thousands of km/s. Earth-directed CMEs arrive in one to three days and drive the geomagnetic storms behind major aurora — and major satellite and grid trouble.
Understanding CME
Anatomy of an impact
A textbook geoeffective event unfolds in acts: flare flash and radio blackout (minutes); solar energetic particle onset (tens of minutes, polar routes and spacecraft affected); CME shock arrival slamming the magnetosphere (a sudden impulse magnetometers register worldwide); then hours of storm main phase as southward field erodes the dayside magnetopause — sometimes exposing GEO satellites to the raw solar wind — and loads the tail, firing substorms and aurora. Recovery takes days; the thermosphere's drag hangover, longer.
The constellation-age stakes
A 2022 storm — moderate by historical standards — famously downed a batch of newly launched satellites still at low insertion altitude, the clearest demonstration yet that space weather is now an operational line item. Studies of Carrington-class recurrence put worst-case economic exposure in the trillions across grids, aviation, navigation and orbital fleets, which is why heliophysics fleets, upstream monitors and storm-hardened design standards keep growing.