On the periodic variations of secondary cosmic rays and the geomagnetic Pc4 pulsations in BMAr

Abstract. In a set of balloon flights in the Brazilian magnetic anomaly region (BMAr) short time periodic variations were observed, i.e. pulsation, of secondary charged and neutral particle fluxes, X- and <gamma>-ray fluxes with amplitudes of about 2–4%. The pulsations are accompanied by the geomagnetic Pc4 pulsations and have similar periodicity. The phenomenon was observed over various local times and in quiet and disturbed magnetospheric conditions. One of the explanations of this effect, i.e. periodic variation of local cut-off rigidity, and following pulsations of primary and secondary cosmic ray intensity is suggested.