Extraordinary waves exhibit rare long-skip propagation, compared to ordinary waves, which travel shorter distances
Independently propagating, elliptically polarized waves created in the ionosphere✓Bonne réponse
Long-path and short-path waves
Refracted rays and reflected waves
Explication
The Earth's magnetic field makes the ionosphere birefringent, so a wave entering it propagates as two independent characteristic modes — the ordinary and the extraordinary wave — which are elliptically polarized in the general case and see different refractive indices, so they follow different paths and suffer different absorption. The names have nothing to do with unusually long skip, with long versus short path, or with a distinction between refraction and reflection.