Splitting of the Doppler frequency shift of bi-static backscatter signals during the Sura experiments

The experimental studies of the specific behavior of small-scale artificial ionospheric irregularities at midlatitudes, performed using the Sura HF heating facility, are analyzed. The observations were performed in September 2006, using the method of bi-static backscatter by artificial ionospheric irregularities on the Armavir-Sura-St. Petersburg and Samara-Sura-Rostov-on-Don diagnostic paths. It has been detected that the Doppler frequency shift of scattered signals at 3–7 Hz was split on the Armavir-Sura-St. Petersburg path from 1500 to 1600 UT on September 6, 2006. The simultaneous measurements on the Samara-Sura-Rostov-on-Don path indicated that only one signal of bi-static backscatter was present. An analysis of the experimental data, performed using the numerical simulation results, indicated that the ordinary and extraordinary polarization modes of bi-static backscatter signals could be simultaneously observed on September 6, 2006, on the Armavir-Sura-St. Petersburg path.