Structured pulsations in the frequence range 0–5 Hz such as pearls are of common occurrence and therefore are well studied. The pearls appear on magnetograms as a series of wave packets. Despite numerous studies, the question of the cause of such modulation remains open. Another type of modulated 1, which appears on sonograms as a series of shapeless clouds without a pronounced internal structure (unstructured 1) is less studied. At the early stages of research, unstructured 1 were considered primarily in the context of the magnetospheric response to the impact of a slow shock front on the magnetopause (SI event). Later, it was shown that SI is not a necessary condition for generation of this subclass of 1. In this paper, we investigate the unstructured modulated 1 observed both before and after SI. Using a favorable position of the GEOTAIL and THE satellites, we show that there are pressure variations with a period of 12 minutes inside the magnetosphere synchronized with the clouds of unstructured 1. There are no pressure variations on satellites in the solar wind. Instead, the satellites record variations with the same period in the IMF. Based on observations, we propose a scenario of the phenomenon.
V. V. Safargaleev (Wed,) studied this question.