The first results of investigations of earth current pulsations in the range of periods of 1 to 15 seconds are presented. Data of earth current stations located in the Arctic (5 stations), in the Antarctic (2 stations), and in middle latitudes of the USSR (10 stations), as well as data of high‐sensitivity installations for magnetic‐field (Z) registration at 3 stations, were used. Several characteristic types of pulsations were defined in this range of periods, and their correlation with phenomena in the high atmosphere was studied, among them: (a) short irregular pulsations (T∼1–15 sec) composing the microstructure of several forms of macroscopic disturbances of the magnetic field and showing a close correlation with aurora; and (b) pulsations of the ‘pearl’ type (T∼1–4 sec), distinguished by their regular form and showing a correlation with cosmic‐ray intensity bursts in the stratosphere.The main features of magnetic‐storm microstructure, as well as the microstructure of SSC, are given. The importance of the occurrence during magnetic storms of ‘pulsations with diminishing periods’ and correlation studies with high‐atmosphere phenomena is stressed. The dependence on local time of the fine structure of SSC is described. Contrary to some theoretical expectations the time difference between the first movements due to SSC was found to be very small; the movements may even have been simultaneous. For the Argus III explosion the onset time of oscillation was fo