Yu.K. Kalinin, A.L. Dzvonkovskaya

The data of unique experiment on research of properties of a round-the-world signal (RWS) of HF radar near to his antipode in conditions of realization of nuclear explosion are considered. Measurements were made by autumn of 1971 on a pre-production model of the HF radar located in the south of Ukraine. Characteristics of this radar allowed to carry out round-the-clock registration of RWS on frequency of 16 MHz, including due to nonlinear effects. The round-the-world line passed through Indonesia, Australia and reached antipode point approximately on 2 thousand in km to the south of the French range of nuclear tests on atolls Mururoa and Fangataufa. Cited the data on occurrence of multiple RWS after carrying out of nuclear explosion on this range, and also results of experimental researches of RWS which times of arrival included an interval of time of realization of nuclear explosion near to his antipode. The hypothesis that occurrence of multiple RWS can be caused by occurrence as a result of the nuclear explosion of negative indignation of an ionosphere reducing losses of energy of a RWS signal because of dispersion of macroscale ionosphere irregularities in antipode of area is proved. Hypothetical interpretation of results in a number of specifications of possible influence ionosphere irregularities in the field of an antipode of a radar on power of RWS. The first RWS (RWS-1) was registered as a pulse with a time delay 138 ms. One-hop oblique backscatter sounding (OBS-1) signal was formed or due to a back petal of the reception aerial and the main petal transmitting, or on the contrary. At a reverser of the reception aerial signal OBS-1 essentially grew, and was accompanied by supervision two-hop oblique backscatter sounding signal simultaneously essentially the amplitude of RWS-1. Selection of a RWS was made to three attributes: 1) on the time delay RWS-1 equal 138 мс; 2) on reduction of amplitude RWS-1 at a reverser of the reception aerial; 3) on increase in amplitude of signals OBS at a reverser of the reception aerial. After nuclear explosion the alarm picture quickly changed. Contain with signal RWS-1 increasing on amplitude within several hours signals RWS-2 on a time delay 76 ms and RWS-3 on a time delay approximately 15 ms were observed. From all interpretations of the given experiment it is necessary to allocate some fundamental questions (namely, about delay RWS-1 equal 138 мс; about the sizes antipode «stain» of focussing; about at-tenuation of waves in the field of an antipode) which result in interesting hypotheses. The geophysical and radiophysical effects caused by an arrangement of nuclear explosion near to an antipode of a radar, recording RWS in a HF range are analysed. The hypothesis that occurrences of multiple RWS can be correlated to the phenomenon of reduction of contrast ionosphere irregularities in the field of an antipode under action of a shock wave of nuclear explosion is proved.