Heater‐induced cavities as optical tracers of plasma drifts

A new technique is used to measure F region plasma drifts at night. The technique involves observing the motion of density cavities generated by high‐power radio waves in the ionosphere. The airglow signature of the cavities is recorded and analyzed with a ground‐based, low‐light‐level imaging system. The heater‐induced cavity optical tracer method is capable of providing velocity information with an error less than 1 m/s and a time resolution better than 60 s.