What causes tropospheric ducting?

Tropospheric ducting is a highly sought-after propagation mode that occurs in the lowest layer of the atmosphere (the troposphere) where all of our weather happens. It allows VHF, UHF, and microwave signals to travel hundreds of miles beyond the normal visual line of sight. This phenomenon is caused by a temperature inversion, which happens when a layer of warm air becomes trapped above a layer of cooler, denser air near the surface. This inversion creates a 'duct' or channel that bends radio waves back toward the Earth instead of letting them escape into space. Distractors like solar flares, lightning, and tornadoes might sound like powerful weather or space events, but they do not create the stable atmospheric layering required to trap and duct radio signals. Sunspots affect the ionosphere, not the troposphere.