Why is radio reception often better at night than during the day?

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Diagram of Earth's atmosphere layers-troposphere, stratosphere, mesosphere, and thermosphere-showing how temperature and air pressure change with increasing altitude, with key features like the ozone layer and pressure percentages at various heights. — Ionosphere and magnetosphere The layers of Earth's atmosphere, with a yellow line showing the air temperature at various heights.

Radio reception is often better at night because of changes in the ionosphere, specifically the behavior of the D region.

During the day, solar radiation creates ionization in the D region, which absorbs radio waves and reduces their transmission range. At night, the Sun’s radiation is absent, causing free electrons and ions in the D region to recombine into neutral gases. Because this layer of ionization effectively disappears, radio waves are no longer absorbed or blocked by it. Instead, they can pass through to the higher E region and F layers, which act as mirrors to reflect the signals back toward Earth. This allows radio transmissions to travel much further than they can during the day.123