>>6250926 Preet Shillrara.
>SHOULD be a standing wave
it IS a standing wave (actually a series of them).
If you think that a standing wave must be the same exact frequency all the time then you must be mistaking the earth's Schumann cavity for a rigid, unchanging structure (the only time a resonant frequency remains constant). The small fluctuations in the ionosphere's parameters caused by variations in solar output (height above the Earth's surface, conductivity etc…) cause the frequency of the standing waves to vary slightly, much like moving the slide on a trombone (changing the resonant chamber size) changes the frequency produced.
>Not sure what it means,
that's obvious, but you know it means something don't you
it's a pity science education has diminished to this point