The Magnetic Field of the Ionosphere and Magnetosphere

One contribution to the magnetic field of the Earth often varying rapidly in time and space has its sources in near Earth space. These magnetic signatures are from electric current systems in the magnetosphere and ionosphere, driven by solar radiation or thermospheric winds.

During quiet periods the amplitude of these external contributions are about 20 nT at mid-latitudes, increasing to more than ten- or hundred-fold during geomagnetic storms at all latidudes. The quantification of these geomagnetic sources allows the investigation of the near Earth space.