Report from IUGG Assembly: IAGA session on electromagnetic coupling within the atmosphere



Electromagnetic fields of low frequencies with periods smaller than about 1 hour can easily penetrate from the lower into the upper atmosphere, and vice versa, with very short time constants. Therefore, they can serve as a coupling link to transfer energy from one region into another. One prominent example is the transfer of kinetic energy of the solar wind into thermal energy of the upper atmosphere via a magnetohydrodynamic generator process in which the electric convection field of the magnetosphere is the link between magnetosphere and ionosphere by the driving of high-latitude electric currents within the dynamo region.

Another example is the electric coupling between the ionospheric E and F layer via the electric polarization field of the Sq current. Here, the surf's thermal energy input into the lower and the middle atmosphere is redistributed via the generation of tidal waves, associated electric fields and Sq currents at E layer heights, and the driving of F layer winds by the polarization field mapped upward into the F layer. Finally, the thunderstorm electric fields within the troposphere can map into the magnetosphere, and they may be responsible for field-aligned irregularities in that region, or electric fields of magnetospheric origin may map downward into the lower atmosphere.