1. Introduction

[2]  The investigation of relativistic electron precipitations (REPs) and the relativistic electrons (REs) in the Earth radiation belts began nearly 40 years ago by the indirect measurements of the bremstrahlung X rays generated by REPs [Charahchan et al., 1965], by indirect ground LF monitoring [Beloglazova and Beloglazov, 1982; Remenets and Beloglazov, 1985] (part of the Beloglazova and Beloglazov paper should be revised according to the results of the LF inverse problem solving) and by direct satellite measurements of the REs [Baker et al., 1997; Callis et al., 1991; Pesnell et al. 1999]. It is convenient to subdivide the REPs according their energy E: the moderate energetic relativistic electrons (MEREs) with E < 1 MeV, the high energetic relativistic electrons (HEREs) with 1 MeV  < E < 10 MeV [Baker et al., 1997; Pesnell et al., 1999] and the ultrarelativistic electrons (UrEs) with E > 10 MeV [Remenets and Beloglazov, 1999] for which there are no reliable satellite measurements. The interest in these kinds of electrons is not only of scientific value in connection with magnetosphere-atmosphere problems but is a practical one as well. The problem of telecommunication system protection from these HEREs is urgent now [Baker et al., 1997]. In connection with the ultrarelativistic electron (UrE) events [Remenets, 1994, 1997; Remenets and Beloglazov, 1985, 1985a, 1992] the problem of human protection in the low-middle atmosphere and the magnetosphere from the bremstrahlung X and gamma rays may be is of importance.

[3]  The problem of the blockade of ground and air radio systems (for short and long waves at high latitudes for some hours or days in connection with HERE and UrE precipitations has not been discussed in the literature up to now yet. Investigation of the problem of ozone depletion as a result of the REPs has been reported [Callis et al., 1991; Pesnell et al., 1999; Roldugin et al., 1998, 2000]. The methods used in the investigations are qualitatively different. Baker et al. [1997] and Callis et al. [1991] measured the electron fluxes in the radiation belts but did not perform the direct measurements of the electrons precipitating. Pesnell et al. [1999] fulfilled the last kind of measurements.

[4]  In our work the direct measurements of the REPs are not available, and the solution of the inverse LF problem was used for the analysis of LF disturbances due to the EPs on some radio traces. The first results of this kind have been published by Beloglazov et al. [2000], Remenets [2000a, 1997], and Remenets and Beloglazov [1985, 1992]. The purpose of the present work is to summarize the results for all of the so-called powerful disturbances (PwDs) generated by the UrEPs during 1974-1992.