Rocket-borne wave measurements in the dayside auroral oval

VLF and ELF waves were measured on two rocket payloads launched into the dayside auroral oval on Dec. 18, 1974, and on Jan. 11, 1975. The correlation of the VLF hiss intensity with the fluxes of precipitating electrons above 500 eV on short spatial and time scales was often poor, even when a positive slope existed in the electron phase space density. During the flight in 1975, distinct features were observed at the lower hybrid frequency; the frequency of this emission was used together with an independent density measurement to determine the relative concentration of O(+) to the heavier ions NO(+) and O2(+). It was found that the density of NO(+) or O2(+), which could not be distinguished, is enhanced over expected values between 150 and 400 km altitude. Broadband electrostatic and electromagnetic waves were observed after the barium-shaped charged explosion in 1975; the observed lowering of the auroral VLF hiss cutoff due to the barium is consistent with either ducting of VLF hiss emissions along the enhanced density duct produced by the barium or with local generation VLF hiss during the barium injection.