The Sun constantly streams charged particles — the solar wind — outward through the solar system. Earth's magnetic field normally deflects this wind around the planet, carving out a protective bubble called the magnetosphere. But when the wind is fast and dense, and when the interplanetary magnetic field it carries points south (negative Bz), it can "reconnect" with Earth's field on the dayside, opening a door that lets solar particles pour down into the polar atmosphere — producing aurorae, and driving the electrical currents that a global monitoring network exists to track.
Real-time solar wind data used for storm warnings comes from spacecraft parked about 1.5 million km sunward of Earth at the L1 Lagrange point — such as NASA/NOAA's DSCOVR — giving grid operators and satellite controllers roughly 15–60 minutes of advance warning before a disturbance arrives.
Solar wind streams past Earth and either gets deflected around the magnetosphere or, when the interplanetary magnetic field points south, reconnects and funnels particles into the polar atmosphere — the physical process behind the Kp and Dst indices that grid operators and satellite controllers watch.
The magnetosphere's teardrop shield compresses under wind pressure and opens to reconnection when Bz turns negative, driving the Kp storm index, the Dst ring-current index, and downstream risk to power grids and satellites.
Adjust solar wind speed and IMF Bz to see the shield compress and aurora brighten, launch a simulated CME to watch a shock pulse spike the storm indices, and switch to the grid/satellite view for a plain-language risk read-out.
NOAA's Space Weather Prediction Center issues real storm watches from data gathered roughly one hour before impact by spacecraft parked at the L1 Lagrange point, giving grid operators just enough time to reconfigure networks.