My personal way of visualizing the various “layers” of the Ionosphere is not to see them as “layers” but as very thin, and very wide clouds. A simple way to do this is to imagine a Laser light show at a rock concert. When the Laser sweeps horizontally, wherever the “smoke” is more visible equates to a heavily Ionized cloud “layer”, & where there are gaps or holes, these equate to where there is little Ionization.
To visualize the D, E, & F Layers purely as “Layers” may lead to the misconception that they give constant propagation characteristics over a wide area, when in fact, as Stewart G0LGS mentioned earlier, a few hundred Metres difference in location can make a huge difference at VHF. The same difference in propagation can also be experienced at HF, although the distances between different experiences tend to be larger.
This effect is felt more with E layer propagation as it is nearer to the ground (hence covering shorter distance in a single “hop”) & more short lived than the often sustained & widespread openings via F2 at Solar Maximum.
It’s all good fun though
Thanks & 73,