The effects of a powerful high-frequency electromagnetic wave transmitted in the ordinary mode from the European Incoherent Scatter (EISCAT) ionospheric modification facility up to the daytime ionospheric F region have been studied with the EISCAT-UHF radar system. This is one of the first tristatic EISCAT-UHF incoherent scatter experiments, in which the excited Langmuir and ion acoustic fluctuations are measured simultaneously at scattering angles near parallel (Troms¿ site), ~22¿ (Kiruna site), and ~31¿ (Sodankyl¿ site) to the geomagnetic field. We present measurements of the spectral structure anad temporal evolution with a maximum resolution of 13 ms, at the different scattering angles. For the first time, up to five cascade lines in addition to the decay line in the Troms¿ HF-enhanced plasma line and well-developed cascade type plasma lines in Sodankyl¿ were observed. In spite of low background electron temperature, and hence negligible electron Landau damping parallel to the geomagnetic field, the excited plasma turbulence varied considerably. ¿ American Geophysical Union 1995