According to the pioneer work of Sir E. Appleton the vertical structure of the terrestrial ionosphere may be devided into different layers (D, E, F1, F2) with different physical characteristics. The layers are primarily characterized by its height and peak electron density. Typical plasma frequencies /electron densities are in the order of 10 MHz /10¹² electrons / m³.

Shown are here global maps of the peak electron density of the F2 layer and related electron density maps at selected altitudes. The figures provide a first estimation of the three dimensional electron density distributions around the globe.

The spatial plasma distribution is generated from actual TEC maps by applying a first version of the empirical electron density model NEDM-v1. In correspondance with the update rate of TEC maps the time resoultion of the 3 D images is 5 minutes.