CME Early Warning: L1 Lead Time Simulator

Early-warning mode

CME launch

CME speed 900 km/s

Idle. Set a CME speed and launch an eruption.

Transit progress

Distance remaining

150.0M km

Est. transit time

–

L1 lead time

–

This run — damage

Satellites hit

–

Grid status

–

Estimated damage cost

–

Cumulative comparison

Unprotected hits (avg $)

0 runs

Protected hits (avg $)

0 runs

How the lead time works

A flare's light and X-rays reach Earth in about 8 minutes — that's confirmation an eruption happened, but it says nothing about whether the slower-moving plasma cloud is actually aimed at Earth. The CME itself takes anywhere from roughly half a day to several days to cross the 150 million km gap, depending on how fast it left the Sun.

A spacecraft parked at the Sun–Earth L1 Lagrange point sits upstream in the solar wind, so it directly samples the CME's magnetic field and particle density as the cloud sweeps past — typically 15 to 60 minutes before the same plasma reaches Earth's magnetosphere. That window is short, but it's enough time for satellite operators to drop vulnerable systems into safe mode and for grid operators to brace transformers against the geomagnetically induced currents that follow.

No L1 warning — the impact arrives with zero notice: satellites and the grid take the full hit unprotected.
L1 early warning — the countdown that starts when the front crosses L1 is the entire margin operators get to act before the same cloud reaches Earth.

Sun Earth CME cloud L1 sentinel

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.