Ionospheric dynamo region

In the height region between about 85 and 200 km altitude on Earth, the ionospheric plasma is electrically conducting. Atmospheric tidal winds due to differential solar heating or due to gravitational lunar forcing move the ionospheric plasma against the geomagnetic field lines thus generating electric fields and currents just like a dynamo coil moving against magnetic field lines. That region is therefore called ionospheric dynamo region.[1] The magnetic manifestation of these electric currents on the ground can be observed during magnetospheric quiet conditions. They are called Sq-variations (S=solar; q=quiet) and L-variations (L=lunar) of the geomagnetic field. Additional electric currents are generated by the varying magnetospheric electric convection field. These are the DP1-currents (the auroral electrojets) and the polar DP2-currents. [2] Finally, a polar-ring current has been derived from the observations which depends on the polarity of the interplanetary magnetic field.[3] These geomagnetic variations belong to the so-called external part of the geomagnetic field. Their amplitudes reach at most about 1% of the main internal geomagnetic field Bo.

  1. ^ Chapman , S.J. and J. Bartels, „Geomagnetism“ , Clarendon Press, 1951
  2. ^ Akasofu, S.I., "Physics of Magnetospheric Substorms", Reidel, Dordrecht, 1977
  3. ^ Heppner, J.P., in Dyer, E.R. (ed), "Critical Problems of Magnetospheric Physics", Nat. Acad. Sci.,Washington, D.C., p. 107. 1972