In rec.radio.amateur.antenna Jeff Liebermann wrote:

That's why I posted my rant. The idea that VLF signal will reflect or
refract off the D-layer is new to me. I had always assume that
everything with a wavelength longer than the BCB is ground wave.
Apparently not.

In this article there is a nine chart that shows propagation modes versus
frequency with links to explainations.

https://en.wikipedia.org/wiki/Radio_propagation#Modes


--
Jim Pennino