ABSTRACT
“Space weather” concerns the rapid variations of the magnetic field due to electric currents in the Earth’s ionosphere and magnetosphere (including secondary fields due to electromagnetic induction in the Earth’s interior). The spatial power spectrum of the geomagnetic field, often called geomagnetic spectrum or Lowes–Mauersberger spectrum is a useful way of characterizing the spatial behavior of the Earth’s magnetic field. When analysing data taken at altitudes of several thousand kilometers where nondipole contributions to the geomagnetic field become less important, it is convenient to approximate Earth’s internal field by means of a dipole. Describing Earth’s magnetic field by an inclined dipole is valid at altitudes greater than several Earth radii. Earth’s magnetic field affects the motion of charged particles. As a consequence, processes in the Earth’s ionosphere and magnetosphere are naturally organized with respect to the geomagnetic field. The International Geomagnetic Reference Field model describes the temporal evolution of the geomagnetic field using a linear time dependence within five years.
