ABSTRACT
First of all, the near-the-Earth environment can rarely be quiet, as there are many perturbations including those having the nature of waves. The WDs accompany the perturbations of the Sun, geospace storms, powerful atmospheric processes, volcanic activity, earthquakes, and so on. As mentioned in Chapters 2 and 3, WDs are generated also by the launches and flights of space vehicles (SVs) and rockets, powerful explosives, and other high-energy sources affecting the near-the-Earth environment. We should note that the frequency of the occurrence of the WDs is very difficult to estimate. It depends on the methods of detection of the WDs, the sensitivity of the detectors that record the relative amplitude d = ΔN/N of the electron density of N variations, the frequency of occurrence of the sources of these WDs, as also other factors. We can only declare that the frequency of appearance of the WDs does not exceed several tens of percent from the entire time of observations of the near-the-Earth environment (see, e.g., Refs. [5,19]).
