How does the D layer ionization density compare to that of the F layer?

The D layer of the ionosphere has a lower ionization density compared to the F layer due to its unique characteristics and formation processes. The D layer is typically formed during the daytime and is influenced mainly by the absorption of solar radiation at lower altitudes, which leads to a relatively lower concentration of ions. This ionization occurs at altitudes roughly between 30 to 90 kilometers.

In contrast, the F layer, which is located at higher altitudes (approximately 150 to 1,000 kilometers), is characterized by stronger ionization due to the more intense solar radiation it receives, particularly at higher frequencies. Consequently, the F layer can sustain a higher density of ions and electrons, enabling it to support long-distance radio communications.

This fundamental difference in the ionization processes and conditions prevailing at different altitudes explains why the density of the D layer is lower than that of the F layer.