Sun, Wind, and Polar Rain:
The near Earth plasma environment

Thomas Ulich

Department of Physical Sciences, University of Oulu,
Linnanmaa, FIN-90570 Oulu, Finland


Since the beginning of the satellite era in the late 1950s the environment of the Earth, i.e., the magnetosphere, has been extensively examined. It has been discovered that the shape of the magnetosphere is a direct consequence of the interaction between the solar wind and the geomagnetic field. We give an introduction to the magnetic environment of the Earth and show how it is stabilized by a system of currents and electric fields. We discuss geomagnetic disturbances such as substorms. Even though many magnetospheric processes are nowadays well understood, those triggering the series of events leading to auroral substorms have not been clearly identified by now.