Solar Wind, Heliosphere & Space Weather: Structures & Vocabulary

The solar wind is a continuous outflow of charged particles from the Sun's corona that fills a vast bubble around the Sun called the heliosphere. Variations in the solar wind, magnetic field, flares, and CMEs create space weather that can alter Earth's magnetosphere and affect technological systems.

The corona is hot enough that some plasma escapes the Sun's gravity and accelerates outward along open magnetic field lines. As the Sun rotates, its magnetic field is carried outward by the flowing plasma into a spiral structure. Disturbances such as high-speed streams and CMEs compress or reconnect with planetary magnetic fields.

Spacecraft measure solar-wind speed, density, temperature, and magnetic field directly. Auroras, geomagnetic storms, radio disruptions, satellite drag, and induced currents in power systems correlate with changes in solar-wind conditions and eruptive solar activity. Voyager spacecraft have crossed major heliospheric boundaries.

Fast and slow solar-wind streams differ in speed, density, source regions, and composition. The heliosphere contains the termination shock, heliosheath, and heliopause, while the Parker spiral describes the rotating Sun's wound-up interplanetary magnetic field. Planetary magnetospheres carve local structures inside this flow.