5. Conclusions

[31]  1. Ionospheric effects of the magnetic storm determined by the Doppler measurements of the signals scattered by AIT correlate well to the behavior of the southward B_z component of the interplanetary magnetic field and variations in the geomagnetic field on the Earth. It is found that at heights of the F region of the midlatitude ionosphere in undisturbed conditions the electric field and the drift velocity of irregularities corresponded to the typical values ~1 mV m^-1 and 20 m s^-1, respectively. During the magnetic storm these values increased up to values of ~8.6 mV m^-1 and 186 m s^-1, respectively, the latter values better corresponding to the values typical for the high-latitude ionosphere.

[32]  2. The comparison of the appearance of sporadic trains of the quasiperiodic variations in DSF of HF signals to the behavior of the interplanetary magnetic field and variations of the magnetic field components on the Earth as well as the estimates of d H of the geomagnetic field based on the Doppler measurements lead to the conclusion that the oscillations of the Doppler shift of the scattered signal frequency are due to the wave processes related to the propagation of lateral magnetohydrodynamic waves intensified during a magnetic storm.

[33]  3. Using the diagnostics of the ionospheric channel with the help of the aspect scattering of radio waves at artificial small-scale magnetically oriented irregularities, the conditions of formation of the HF signal field in the upper ionosphere in the presence of a sporadic E layer are studied. It is demonstrated that at distant paths the E_s layer may play an important role in formation in the upper ionosphere of the radio wave field at frequencies exceeding MUF of the standard hop propagation via the F region of the ionosphere.

[34]  In conclusion, we note that in parallel to the measurements of the aspect scatter of radio waves at the magnetically oriented small-scale irregularities of the plasma, in the period from 9 August to 23 August we conducted studies of the characteristics of the artificial radioemission of the ionosphere (ARI) at the reception point located in 1.5 km from the SURA facility. The observation period covered both quiet (before 17 August) and disturbed (18-23 August) ionospheric conditions. A detailed discussion of the results obtained is out of the scope of this paper and will be presented in a separate publication. Here we only mention briefly that according to the preliminary processing of the experimental data obtained, in magnetically disturbed conditions an increase by 4-8 dB in two main components of the emission is detected [Frolov et al., 2001]: DM (downshifted maximum, the main spectral maximum in the ARI spectrum shifted down by 10-15 kHz from the pumping frequency) and BUM (broad upshifted maximum, the wide-band maximum of the emission at frequencies above the pumping wave frequency the generation of which is observed when the frequency of the powerful wave exceeds the frequency of the harmonics of the electron gyrofrequency in the region of its interaction to the ionospheric plasma). This may indicate to a considerable influence of ionospheric disturbances on the conditions (mechanisms) of ARI generation. For more detailed consideration of the nature of such influence we plan in future to conduct new experimental studies.