We report the first evidence of artificial ionospheric plasmas reaching sufficient density to sustain interaction with a high‐power HF pump beam produced by the 3.6 MW High‐Frequency Active Auroral Program (HAARP) transmitter in Gakona, Alaska. The HF‐driven ionization process is initiated near the 2nd electron gyroharmonic at 220 km altitude in the ionospheric F region. Once the artificial plasma reaches sufficient density to support interaction with the transmitter beam it rapidly descends as an ionization wave to ∼150 km altitude. Although these initial artificial layers appear to be dynamic and highly structured, this new ability to produce significant artificial plasma in the upper atmosphere opens the door to a new regime in ionospheric radio wave propagation where transmitter‐produced plasmas dominate over the natural ionospheric plasma and may eventually be employed as active components of communications, radar, and other systems.

Observations of HF‐induced artificial optical emissions at the 3.6 MW HAARP facility show unexpected features not seen at the previous 960 kW level. Optical emissions often form a bright rayed ring near the 10% power contour surrounding a central disk with a sharp edge near the 50% power contour. Artificial bottomside layers in ionograms and positive perturbations in total electron content suggest that the bullseye optical patterns are associated with localized enhancements in plasma density below the main F layer. Ray tracing shows transmitter power concentrates in an annular structure consistent with the optical observations. Estimated ionization rates are well within the power available from the transmitter and agree well with the observed intensity of N2+ 427.8 nm emissions. We conclude that the optical bullseye patterns are a refraction phenomenon and an indicator of ionization production within the transmitter beam.