Model ionosphere for D region at summer noon during sunspot maximum

A model ionosphere, comprising electron-density and collision-frequency distributions for the midlatitude D region at summer noon during sunspot-maximum conditions, has been produced which will give satisfactory results for propagation at low and very low frequencies. The electron-density distribution above 68 km was based on a distribution, measured in a rocket, which was altered until fullwave calculations using it gave propagation parameters in agreement with the average observed values. Below 68 km, a C layer was found necessary to give the best fit to measured ground-interference patterns at 16 kHz. A comparison is also shown between a measured pattern of this kind and one calculated from the rocket distribution, which was obtained on the same day.