Modification of the auroral E-region with powerful HF waves

Abstract: Data from an ionospheric heating experiment in Tromsø have beenanalyzed. The experiment was carried out during auroral conditions inOctober 2006. Beside data from the EISCAT UHF radar also opticaldata were recorded with the ASK (auroral structure and kinetics) instrumentand enhancements of backscattered power from the E-regionwere studied. Two simultaneous layers of instability with an altitudeseparation of 5 km are observed at an altitude of 120 km. Thetwo layers differ in their spectral characteristics and show different timeevolution. For one heating cycle it was also found that auroral processescorrelate to the strength of enhancements and the characteristics of theion line spectra.