The screening of micropulsation signals by the atmosphere and ionosphere

A study is made of the screening effect of the atmosphere and ionosphere which lets only part of a micropulsation signal reach the ground. Using four ionospheric models, we find that the previously predicted polarization rotation by the ionosphere occurs under all conditions but that at night the ionosphere reflects much less of the incident energy, i.e., that it becomes a much better energy sink. We also find that the ionosphere-atmosphere system strongly attenuates signals with large cross-field wave numbers . This results in the observation of only the gross structure of magnetospheric wave fields on the ground.