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How does the solar wind compress the dayside of Earth’s magnetosphere?
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Ionosphere and magnetosphere
The layers of Earth's atmosphere, with a yellow line showing the air temperature at various heights.
The solar wind compresses the dayside of Earth’s magnetosphere by exerting a dynamic pressure that balances the pressure of the geomagnetic field at a distance of approximately 10 Earth radii (about 65,000 km).123
This interaction occurs through the following mechanisms:
- Pressure Equilibrium: As the solar wind—a flux of charged particles from the Sun—approaches Earth, it encounters the planet's magnetic field. At the dayside boundary, the solar wind's pressure is countered by the magnetic pressure of Earth's field, creating an equilibrium region known as the magnetopause.13
- Magnetopause Current: When solar wind particles strike the geomagnetic field, they are deflected by the Lorentz force. This deflection generates the magnetopause current (or Chapman-Ferraro current) system, which flows in a sheet across the dayside. This current system effectively confines the terrestrial magnetic field within the magnetosphere, preventing it from expanding indefinitely into space.4
- Bow Shock: Before reaching the magnetopause, the supersonic solar wind encounters a bow shock, a region of magnetic turbulence and shock waves that slows and deflects the solar wind plasma around the magnetosphere.123