What phenomenon describes the downward turbulence created by helicopters?

The phenomenon that describes the downward turbulence created by helicopters is known as rotor downwash. As a helicopter's rotor blades spin, they create lift by moving air downwards. This downward movement of air is what constitutes downwash. Because this air is pushed down, it can create a turbulent and sometimes unstable flow of air in the surrounding area.

Rotor downwash plays a crucial role in understanding helicopter operations, particularly during takeoff and landing, where the effects of the downwash can influence the ground environment, including dust, debris, or weathering of surfaces immediately beneath the rotor system.

Jet blast refers to the high-velocity exhaust produced by jet engines, which is different from the rotor-induced turbulence of a helicopter. Induced roll is a term more associated with the effects of aileron input on an aircraft's roll axis rather than the turbulence generated by rotor downwash. Prop wash, while it also describes airflow caused by spinning propellers, specifically pertains to airplanes that use propellers rather than rotor blades like those in helicopters. Thus, rotor downwash is the most accurate description of the specific turbulence generated by helicopter rotors.