The space environment around the Earth is often thought of as a quiescent vacuum, while in reality it is filled with plasma or ionized particles with energies that range from a few eV to above a MeV. The solar wind—which is plasma escaping from the Sun—can warp the terrestrial magnetic field, producing a magnetosphere filled with this solar wind plasma as well as plasma from the portion of the upper atmosphere called the ionosphere. The entry of the solar wind plasma is modulated by the interplanetary magnetic field (IMF) that is carried by the solar wind from the Sun.
The entry of this solar wind plasma and its energy into the magnetosphere can have many significant effects on human activity. For example, the solar wind interaction produces large currents in the ionosphere. Surges in these currents can disrupt terrestrial power grids. The precipitation of energetic particles into the ionosphere can modify its conductivity and thereby affect communications. The induced heating of the ionosphere can create enhanced outflows of plasma from the ionosphere, which in turn can increase drag on satellites and alter their position relative to their desired orbits. The presence of energetic particles that form the radiation belts and the ring current are also important as they are a significant radiation hazard to spacecraft electronics.