Optical ring formation and ionization production in high‐power HF heating experiments at HAARP

Abstract

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 N 2 + 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.