1. Introduction

[2]  It is widely known that the most effective and (under the current level of technical development) the only way to defend the Earth from the dangerous space objects (DSO) is using rocket nuclear technologies [see, e.g., Simonenko et al., 2000]. Studying abilities of this way one should pay attention to the phenomena accompanying space nuclear explosions (SNE) and to the following limitations in its organization [Batyr et al., 1996]. The matter is that SNE in the near-Earth space are accompanied by rather intense geophysical phenomena with their following strong impact on the operability of radio engineering systems of control and communication. Among the most large-scale consequences of SNE (together with the electromagnetic pulse (EMP) [Lobolev, 1997a, 1997b; Semenov and Treckin, 2000], the so-called lower region of the enhanced ionization (LREI) should be considered. The region is formed due to the action of the X ray and penetrating radiation from the explosion at altitudes below the ionospheric E region. The appearance of LREI impacts the radio wave propagation and disturbs normal operation of numerous radioelectronics systems located at a considerably large territory corresponding to the direct visibility from the nuclear charge explosion point.

[3]  Glasstone's [1962] book is one of the first that considered the effects of high-altitude nuclear explosions. It should be noted that in Glasstone's book (as well as in the work by the Lobolev [1997a, 1997b]) the description of the problems of radio wave propagation in the conditions of nuclear explosions is presented fairly briefly and is of a rather qualitative but nor quantitative character. In some publications the analysis of the impact of various SNE factors (X rays, gamma-quanta, neutrons, and beta particles) on the ionization of the lower atmosphere and absorption of radio waves is performed separately [see, e.g., Latter and Lelevier, 1963]. Such approach (being quite reasonable while studying EMP SNE [Karzas and Latter, 1965]) is verified only at the initial stage of the study of radio wave propagation in LREI. In his review dedicated to the impact of nuclear explosions on radio wave propagation, Peterson [1967] noted that during the 1962-1966 period very many papers have been published on this theme however the above indicated problem in no way may be considered as solved.

[4]  The main defects of the studies performed earlier are (1) the absence of complex estimates of radiophysical effects (attenuation, elevation angle, and azimuth refraction, Doppler frequency shift) in the scope of a unite modern physical model of LREI; (2) the absence of the control of the performed calculations accuracy; and (3) very limited comparison of the results of calculations to the experimental data concerning both, various parameters of the lower ionosphere ionization and radiophysical effects.

[5]  This paper, unlike the previous publications, is dedicated to complex simulation of the LREI impact on radio wave propagation with controlled accuracy of the calculations of the main radiophysical effects. The calculation of the parameters of the lower region of enhanced (cold) ionization is performed taking into account the entire radiation spectrum of the high-altitude explosion and fairly complete system of kinetic equations. The simulation is performed for SNE with rather large TNT equivalents (q) distanced from the Earth surface to considerable distances H (above the ionospheric E layer). This distance corresponds to general ideas on the use of rocket-nuclear technologies for the defense of the Earth from DSO. The propagation of radio waves through the magneto-conjugated regions and the ionized region in the explosion point (for ionospheric explosions both have much smaller dimensions than LREI [see, e.g., Lobolev, 1997a, 1997b]) is not considered in this paper.

[6]  The need of developing of such model is due not only to the requirements in obtaining correct estimates of characteristics of radioelectronic systems in the conditions of a straggle against DSO. Such model is needed for a detailed analysis of the experimental data registered during high-altitude nuclear explosions.