Solar Wind
Solar wind is a continuous stream of charged particles — primarily electrons and protons — that flows outward from the Sun's corona in all directions at speeds of 400–800 km/s. This plasma flow carries the Sun's magnetic field into interplanetary space, forming the heliosphere, and interacts with planetary magnetospheres to produce phenomena such as aurorae and geomagnetic storms. Solar wind intensity varies with solar activity, and during coronal mass ejections it can temporarily intensify to disrupt satellite communications, power grids, and GPS systems on Earth.
Properties of the solar wind at Earth's orbit (1 AU)
| Property | Slow Solar Wind | Fast Solar Wind | Unit |
|---|---|---|---|
| Speed | 300–500 | 600–800 | km/s |
| Proton density | ~10 | ~3 | particles/cm³ |
| Proton temperature | ~4 × 10⁴ | ~2 × 10⁵ | K |
| Magnetic field strength | ~5–10 | ~5–10 | nT |
| Electron density | ~10 | ~3 | particles/cm³ |
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Related Terms
Magnetosphere
The magnetosphere is the region of space surrounding a planet where the planet's magnetic field dominates and deflects the charged particles of the solar wind. Earth's magnetosphere is generated by convection currents of molten iron in the outer core (the geodynamo), and it forms a teardrop-shaped shield compressed on the sunward side (to about 10 Earth radii) and elongated on the night side into a magnetotail stretching millions of kilometres. The magnetosphere is essential for life on Earth because it prevents the solar wind from stripping away the atmosphere, and its interaction with solar wind particles produces the spectacular aurora borealis and aurora australis at high latitudes.
Solar Eclipse
A solar eclipse occurs when the Moon passes directly between the Earth and the Sun, casting a shadow on Earth and blocking part or all of the Sun's light. A total solar eclipse, visible from within the Moon's umbra (central shadow), causes day to turn to darkness for up to about 7.5 minutes and reveals the Sun's corona — the otherwise invisible outer atmosphere. Solar eclipses occur at new Moon when the Moon's orbital plane intersects Earth's orbital plane, typically 2–5 times per year worldwide, though any specific location experiences a total eclipse roughly once every 375 years on average.
Inner Planet
Inner planets, also called terrestrial planets, are the four rocky planets of the Solar System — Mercury, Venus, Earth, and Mars — that orbit within the asteroid belt at distances less than about 1.5 AU from the Sun. They are characterised by solid, rocky surfaces with metallic iron cores, relatively small sizes and masses compared to the gas giants, and slower rotation in some cases due to tidal interactions with the Sun. Their proximity to the Sun means they experience intense solar radiation, shorter orbital periods, and in most cases lack large moons, making them distinct in composition and environment from the outer planets.
The term "solar wind" was coined by American physicist Eugene Parker in 1958 in his paper predicting the continuous outflow of plasma from the Sun. "Solar" derives from Latin solaris, from sol ("sun"); "wind" from Old English wind.