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The spectral characteristics of electromagnetic radiation from cloud discharges triggered by groups of model hydrometeors in an artificial thunderstorm cloud are presented on the basis of wavelet analysis. It is found that these characteristics depend on the locations of cells of different polarity relative to the ground, on the location of groups of large hydrometeors in the cloud, and the way they are combined into a common array. The characteristic frequency ranges in the spectrum of electromagnetic radiation of cloud discharges recorded on the Earth’s surface and at the height of an artificial thunderstorm cloud are determined. It is assumed that the bulk of large hailstones will modify the characteristics of the spectrum of electromagnetic radiation of cloud discharges in a thunderstorm cloud in different ways, depending on the movement of these hailstones near the areas of positive and negative charge of the thunderstorm cloud. It is found that the boundary frequencies in the spectrum of signals recorded on the Earth’s surface can reach 400 MHz, while they may achieve 1200 MHz at the height of the cloud. The risk of the impact of pulses of electromagnetic radiation from cloud discharges with the revealed spectral characteristics on digital elements of ground cyberphysical systems and aircraft in frequency ranges of mega- to gigahertz is analyzed.

Results of experimental investigations of an influence of the model hydrometeors on an electromagnetic radiation of the discharge phenomena initiated in an artificial thundercloud have been presented. It was established that the characteristics of an electromagnetic radiation of the cloud discharges initiated by the model hydrometeor groups in an artificial thundercloud depend on the location of the cells of a different polarity relative to the ground, as well as on the place of an introduction of the large hydrometeor arrays into the gap between the cells. It was determined that the character of the registered electromagnetic radiation of the discharge phenomena initiated by the model hydrometeor groups in the artificial thundercloud was close to the character of the powerful bipolar impulses of very high frequency registered for the cloud discharges and during the beginning stage of a downward lightning formation. It was proposed that the arrays of a large hail in a thundercloud could provoke the discharge phenomena significantly modifying the characteristics of the electromagnetic radiation of the cloud discharges. It was experimentally shown that the introduction into the artificial thundercloud of the model hydrometeor groups combined in a common system by the dielectric string can sufficiently decrease a power and the duration of the impulses of an electromagnetic radiation of the initiating discharge phenomena.

Basic provisions of the scientific and engineering fundamentals of the methods of an artificial initiation of the downward lightning and intracloud lightning by the model hydrometeor arrays have been formulated. The key role played by the model hydrometeor size and form on the probability of an artificial initiation of the downward lightning and intracloud lightning has been established. Volume hydrometeors of centimeter size are tailored for such goals. Dividing of the model hydrometeors on the five classes differing on the electric field amplification coefficient has been proposed. Model hydrometeors with the amplification coefficient from 5 to 19 will be the most optimal for an artificial lightning initiation. It was found that the requirements for the sizes and parameters of the model hydrometeor families and to the places of their introduction in a thundercloud will be determined in most by the effect of the earlier appearance of the avalanche corona on the hydrometeors. It discharges the nearest parts of the thunderstorm cells leading to the local decreasing of the field strength, probability of the streamer corona initiation, and its transition into the volume leader. It was determined that the combining of the model hydrometeors in the group by the dielectric string or tape and the simultaneous introduction in thundercloud of some hydrometeor arrays will significantly increase the probability of the artificial initiation of the intracloud lightning and lightning “cloud–ground,” and the successful discharging of a thundercloud. Moreover, the minimal linear sizes of separate hydrometeor groups should be more than several dozens of centimeters. Some variants of the disposition of the model hydrometeor groups in a thundercloud (near the bottom boundary of the thunderstorm cell, inside the thunderstorm cell, and in the space between the thunderstorm cells) when the most optimal conditions for the initiation of the intracloud lightning and lightning “cloud—ground” are provided, have been proposed.

This paper presents the results of an experimental investigation of the influence of model hydrometeor arrays on the initiation and propagation of the spark discharges between the artificial thunder cells of the negative and positive polarity. It is specified that introduction of the negative and positive polarity of the model hydrometeors of different types joined into the array using the various methods into the gap between the artificial thunder cells, leads to the significant growth of the probability of initiation of the spark discharges between the cells and total length of the forming discharge system. It is stated that the model hydrometeors of the cylindrical form joined into the group using the dielectric string or tape are the most efficient for these purposes. The physical picture of formation of the spark discharges by the groups of the hydrometeors between the artificial thunder cells of the different polarity is constructed considering the possibility of formation of the high-current streamer and volume leader discharges.

The results of experimental simulation of the influence of hydrometeor groups on the probability of initiation of spark channel discharges between an artificial thunderstorm cell of negative or positive polarity and the ground were presented. It has been discovered that there is a significant influence of the kind of hydrometeors and the method of their combination into a group on the initiation and stimulation of sparkdischarge propagation from an artificial thunderstorm cell. It has been revealed that injection of the groups of plate-rhombus hydrometeors sharply increases the probability of initiation of channel discharge from a negatively charged artificial cell. It has been established that volume-cylinder hydrometeors display an analogous behavior for a positively charged cell. It has been found that the simulation of accelerated formation of the spark discharge between neighboring hydrometeors in the group is a necessary condition for the initiation and stimulation of the channel-discharge propagation between the cloud and the ground. It has been revealed that a dielectric string or dielectric tape can be used for such purposes. A multifactor physical picture of hydrometeor influence on the initiation and stimulation of the spark channel discharge between an artificial thunderstorm cell and the ground has been proposed. This may result in promising methods of artificial initiation of lightning using arrays of model hydrometeors.

The results of experimental investigation of the influence of model hydrometeor arrays on the stimulation of discharging processes of an artificial thunderstorm cell of negative or positive polarity are presented. It has been revealed that insertion into the thunderstorm cell of model hydrometeors of different kinds brought together in an array by different methods can increase the effectiveness of charged-cloud discharging by several times. It has been established that model hydrometeors of ellipsoid form are most effective for neutralization of the charge of a negatively charged artificial thunderstorm cell. Under conditions of a positive polarity of an artificial thunderstorm cell, its discharge is most effectively provided by model hydrometeors of cylindrical form. It has been revealed that introduction of model hydrometeor arrays also has an effect on the duration of the main discharge stage, during which the artificial thunderstorm cell discharges. It has been shown that the duration of the main stage of discharge initiated by arrays of model hydrometeors of different shapes from a negatively charged artificial thunderstorm cell is several times longer than that for a positively charged cell. The obtained data open up new possibilities for using methods of discharge intensification of a natural thundercloud.

Results of the experimental simulation of lightning initiation processes in thunderclouds by large hydrometeor arrays using artificial clouds of charged water aerosol of negative and positive polarity are presented in this paper. A significant influence of the hydrometeor arrays on the discharge initiation and propagation between the charged cloud and the ground is shown. It is found that cloud polarity has a significant influence on the probability of discharge initiation by the hydrometeor array. It is established that hydrometeors have the most pronounced influence on the discharge initiation in positively charged aerosol clouds. Character types of the discharge phenomena initiated by the hydrometeors in the clouds of negative and positive polarity are found: cloud discharges, channel discharges, and diffuse discharges. It is established that the characteristic frequency ranges in the wavelet spectrum of electromagnetic radiation of such discharge phenomena initiated by hydrometeors have greater values for a negative polarity of a cloud than for a positive one. It is found that the characteristics of the current impulse of the main stage of the discharge between the cloud and the ground forming with the participation of hydrometeors differ from the analogous characteristics for cases in which hydrometeors are absent in the gap between the charged cloud and the ground. Thus, using artificial clouds of charged aerosol opens new possibilities for investigation of the processes of lightning initiation in thunderclouds.