While 9kHz[3e-7/cm] (for an earth mode radio example) is lower than the plasma frequency of the ionosphere, 9MHz[3e-4/cm] (critical so that the ionosphere acts as a waveguide), would this be significantly lower, and hence have a high attenuation--a large imaginary component to the refractive index? If so, would this excite the ionosphere? Genuinely curious