A mathematical description of the electrical coupling and dynamics of plasma structure in the E and F regions is presented. The scale size dependence of eletric field coupling along the magnetic field is examined for a realistic background ionosphere and atmosphere. It is shown that while normalized potentials map reciprocally between two altitudes, the potential disturbance caused by a fixed amplitude plasma density perturbation does not. The magnitude of electrostatic potential created by structured ionization is also shown to be strongly dependent on the altitude of the structure. The existence of plasma density structure at some altitude induces structure at other altitudes along the magnetic field in a scale size selective way. The early evolution of an F region structure that is initially confined in altitude is dominated by parallel diffusion. Low-altitude image structure growth imposed by electrostatic fields mapped from the source is also very rapid; significant image amplitudes are reached in a matter of seconds. The altitude distribution of the evolving structure is strongly dependent on the scale size. At E layer altitudes, where the Pedersen mobility is high and parallel diffusion relatively slow, a preferential scale size for image structure is apparent for typical F region source spectra. This preferred scale size becomes smaller with incresing height. Above about 200 km altitude, however, parallel diffusion becomes increasingly important with height in determining the altitude and scale size distribution of structure resulting from a source at higher altitudes. The parallel diffusive flux can be modified by the existence of local plasma structure perpendicular to the magnetic field. ¿ American Geophysical Union 1990