Doppler shift simulation of scattered HF signals during the Tromsø HF pumping experiment on 16 February

Abstract. Comparisons between bistatic scatter measure-ments and simulation results during the Tromsø HF pumping experiment on 16 February 1996 are made. Doppler mea-surements of an HF diagnostic signal scattered from the field-aligned irregularities (FAIs) in the auroral E-region were car-ried out on the London – Tromsø – St. Petersburg path at 9410 kHz from 21:00 to 22:00 UT. The scattered signals were observed both from natural and artificial ionospheric irregu-larities located in the vicinity of Tromsø. To simulate the Doppler frequency shifts, fd, of scattered signals, a radio channel model, named CONE, was developed. The model allows for ray tracing, group and phase paths, and Doppler frequency shift calculations. The calculated Doppler shifts were analyzed for dependence on the magnitude and direc-tion of plasma velocities in the scattering volume. It was found that the velocity components in the north-south direc-tion are crucial for explaining the Doppler frequency shifts of the scattered diagnostic signals. To simulate fd, real veloc-ities obtained from the EISCAT UHF radar at an altitude of 278 km and from the digital all-sky imager during the exper-iment were employed. The simulation results of Doppler fre-quency shift variations with time are in reasonable agreement with the experimental Doppler shifts of scattered signals on the London – Tromsø – St. Petersburg path. Key words. Ionosphere (active experiments; ionospheric ir