Some techniques for the experimental investigation of the ionosphere

The availability of limited numbers of modern advanced digital ionosondes offers many opportunities to make progress in our understanding of the physics of the ionosphere and in ionospheric forecasting. Some applications are discussed, with particular reference to the role played by conventional ionosondes. These include travelling ionospheric disturbances and the mid-latitude trough; ionospheric absorption, especially in the E and F regions; and the uses of oblique incidence ionograms from the aeronomic point of view. It is also pointed out that there is an enormous amount of satellite data lying unused, which could be examined by groups in smaller countries to yield a great deal of useful information about the ionosphere.