Yu.K. Kalinin – Dr.Sc.(Phys.-Math.), Professor, Main Research Scientist, Institute of Applied Geophysics n.a. E.K. Fedorov E-mail: kalinplat@rambler.ru

A.Yu. Repin – Dr.Sc.(Phys.-Math.), Associate Professor, Director of Institute of Applied Geophysics n.a. E.K. Fedorov (Moscow) E-mail: director@ipg.geospace.ru

E.N. Khotenko – Ph.D.(Phys.-Math.), Scientific Secretary, Institute of Applied Geophysics n.a. E.K. Fedorov (Moscow) E-mail: khotenko@ipg.geospace.ru

A.V. Shchelkalin – Head of Department of Postgraduate Studies, Institute of Applied Geophysics n.a. E.K. Fedorov (Moscow)

E-mail: ipg-conf@yandex.ru

Quasi-spherical structure of ionosphere is a factor which allows the decametric wave propagation below the main ionospheric maximum of ionization. For distances on the ground between radio-source and point of observation that are greater than the half of the terrestrial radius, this phenomenon is called decametric wave guiding on long paths for frequencies below maximum applied frequencies. Well known are guiding structures in the form of large-scale spatial oscillations of wave packets in wave-guides «Earth – F2-region» and «E-region – F2-region» [1, 2]. At the same time it should be noted that decametric wave sliding along ionospheric concave surface is quite competitive with the two mentioned above.

The results of theoretical and partly experimental research are analyzed as well as the properties of the exact solution describing the radiation field spatial structure (created by the ground source) in the area between ground and ionosphere with sharp boundary [3, 4]. It is assumed that such waves (glued to concave ionospheric surface) preserve its structure in smooth ionospheric boundary also. Presented is the analysis of the integration path structure in Watson’s contour integral, that is the model of decametric wave ionospheric guiding on long paths. Various factors influencing the model to keep it closer to reality are estimated. The main difference of the model from previously developed ones of round-world distance-frequency characteristics is that it is unbiased and its round-world signal delay does not depend on frequency.

The analysis of tiny structure of decametric wave radiation field zonal harmonics from point source, which is situated near the boundary between layers, allows elucidating a few features of the structure. The two wave types (namely, spiral and glue) are founded in terms of Watson’s integral - the exact solution of model problem. The point v = k0b divides between the two types. The sections of the integration path denoted as CB form spiral waves reflecting from ionosphere. The sections denoted as CD form glue waves. Its superposition forms sliding waves. The latter stipulates high energetics of round-world waves because of its Imv minimum values. As concluding remark it should be noted that experimentally observed dispersion of round-world signal delay could be explained in case of several mechanisms of signal propagation.

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