When is the ionosphere most ionized?

The ionosphere is created and sustained by ultraviolet radiation and X-rays emitted by the sun. Therefore, the level of ionization in the upper atmosphere is directly tied to the intensity of sunlight hitting it. At midday, the sun is at its highest point in the sky, delivering the maximum amount of direct solar radiation to the ionosphere. This causes the highest concentration of free electrons, leading to peak overall ionization. At dawn, dusk, and midnight, solar radiation is either arriving at an oblique angle, completely absent, or transitioning, meaning the ionization levels are significantly lower than at noon.