Other meanings of Solar wind
Astrophysics
The solar wind is a continuous stream of charged particles—mostly electrons and protons—ejected from the Sun's upper atmosphere. It shapes the heliosphere, drives space weather, and interacts with planetary magnetospheres and comets.
The solar wind originates in the Sun's corona, where temperatures exceed a million kelvin, giving particles enough energy to escape the Sun's gravity. The acceleration to supersonic speeds is driven by the pressure gradient of the hot corona and the expansion of the magnetic field, a process first described by Eugene Parker in 1958. The wind has two primary components: the fast wind (about 750 km/s) emanating from coronal holes, and the slow wind (about 300–400 km/s) associated with streamers and active regions1.
The solar wind inflates a vast bubble called the heliosphere, which extends far beyond the orbits of the planets2. Its boundary, the heliopause, marks where the solar wind meets the interstellar medium; the Voyager 1 and 2 spacecraft crossed this boundary in 2012 and 2018, respectively, providing direct measurements3. The wind's interaction with the interstellar medium creates the termination shock and the heliosheath, regions of turbulent plasma that shield the solar system from cosmic rays.
When the solar wind encounters a planet with a magnetic field, like Earth, it compresses the magnetosphere on the dayside and stretches it into a long tail on the nightside, driving geomagnetic storms and aurorae4. Planets without global magnetic fields, such as Mars and Venus, lose atmospheric particles to the wind, a process that has shaped their climates over billions of years5. Comets, with no magnetic field, exhibit ion tails that always point away from the Sun, a direct visualization of the wind's flow.
Beyond the standard two-component model, the solar wind exhibits a spectrum of transient phenomena, including coronal mass ejections (CMEs) that can create shock waves and drive severe space weather. The wind also carries a magnetic field, the interplanetary magnetic field (IMF), which is frozen into the plasma and spirals due to the Sun's rotation—known as the Parker spiral. Solar wind measurements have revealed that the wind is not uniform but structured by turbulence and waves, affecting cosmic ray propagation. Additionally, the wind's interaction with the Moon's surface produces a tenuous exosphere of sodium and potassium atoms, a process studied by the LADEE mission.
The solar wind is a key driver of space weather and a fundamental component of the Sun's influence on the solar system.
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