What causes "tropospheric ducting"?

Tropospheric ducting occurs due to temperature inversions in the atmosphere. In a temperature inversion, a layer of warmer air traps cooler air near the Earth's surface. This phenomenon can create a reflective or conductive layer in the atmosphere where radio waves can be guided along the curvature of the Earth. As a result, signals can travel much farther than usual, sometimes allowing for long-distance communication over the horizon.

The other choices do not directly relate to the specific mechanism that produces tropospheric ducting. While lightning discharges, solar activity, and severe weather events like hurricanes can affect radio propagation in different ways, they do not create the ducting effect that occurs specifically during temperature inversions. Understanding the role of these inversions is essential for ham radio operators, as it can greatly impact their signal reach and communication capabilities during certain atmospheric conditions.