Regularities of Very Long-Distance Radio Wave Propagation in the Ionosphere

Satellite measurements of plasma-density perturbations induced in the topside ionosphere by high-power HF radio waves from the “Sura” heating facility

“…Hence, the duct is formed not due to the forcing of the plasma out of the heated region along the geomagnetic-field lines, as is assumed in the model calculations mentioned above, but for other reasons, which are unclear at present. Moreover, the formation of ducts in our experiments was observed when a high-power radio wave was reflected at altitudes 200−220 km, whereas the model calculations [15,16] show that the duct can be formed if the reflection altitude of the pump wave is greater than 300 km (for smaller reflection altitudes of the pump wave, the transfer of heat into the topside ionosphere becomes inefficient because of the strong decrease in the heatconductance length [11]). All these comments show that a satisfactory agreement between the theoretical considerations and the numerical calculations based on them and the obtained experimental data has not been reached yet.…”

“…In all the experiments in which the frequency f 0 was close to f 0F2 , the appearance of such perturbations of the plasma density was not observed. This can be a consequence of "infiltration" of the radiated power beyond the ionosphere as a result of a decrease in the plasma density at the center of the antenna beam at altitudes near the level of reflection of the O-mode pump wave in the ionospheric F 2 region, as was considered in, e.g., [11]. Such a decrease in plasma density near the level of reflection of a high-power radio wave was recorded in [12][13][14].…”

Modification of the earth’s ionosphere by high-power HF radio emission: Artificial periodic inhomogeneities and the sporadic E layer

“…In this case, the choice of an extraordinary component of a powerful wave for ionospheric heating is stipulated by the following reasons. It is known that various instabilities are excited when modifying the ionosphere by an ordinary-mode powerful radio wave near its reflection point in the F region, which results in the formation of artificial density inhomogeneities of various scales [21,22]. In this case, the main part of the heating power is lost near the powerful-wave reflection point.…”

Results of studying the sporadic E layer by the method of resonant scattering of radio waves by artificial periodic inhomogeneities of the ionospheric plasma

“…The problem of heating of the E s layer by a high-power HF radio wave was considered in [22][23][24][25][26]. The influence of thermal processes on the parameters of the E s layer and its inhomogeneous structure during the ionosphere modification was analyzed in detail in [24].…”