The solar wind is a continuous stream of particles--mainly protons and electrons in a state known as a plasma--flowing outward from the Sun. High speed solar winds bring geomagnetic storms while slow speed winds bring calm space weather. Forecasting the solar wind is critical to developing forecasts of space weather and its impacts at Earth.
Coronal Mass Ejections (CMEs) are large clouds of plasma and magnetic fields hurled into space from the Sun. The ejected material can travel a million or more miles per hour (500 km/second). Fast CMEs occur more often near the peak of the 11-year solar cycle, and can trigger major disturbances in Earth's magnetosphere. The Sun can eject matter in any direction, so only some of the CMEs will actually encounter Earth.