A magnetosphere is that area of space, around a planet, that is controlled by the planet’s magnetic field. The shape of the Earth’s magnetosphere is the direct result of being blasted by solar wind. It prevents most of the particles from the Sun, carried in the solar wind, from hitting the Earth. The Sun and other planets have magnetospheres, but the Earth has the strongest one of all the rocky planets. The Earth’s magnetosphere is a highly dynamic structure that responds dramatically to solar variations. Life on Earth developed and is sustained under the protection of this variable magnetosphere.

fr/http://science.nasa.gov/heliophysics/focus-areas/magnetosphere-ionosphere/