Generation of Pc5 pulsations during the sign reversal of the IMF B z component

The negative and positive fronts of the IMF B _z component arrived at intervals of 3 h during a strong magnetic storm of May 15, 2005. The occurrence of Pc5 pulsations at these three characteristic instants has been considered based on the WIND satellite magnetic data. Pulsations originated not only during sudden compression SC of the magnetosphere but also during the B _z sign reversal from positive to negative. The IMF B _z sign reversal from negative to positive did not affect the development of pulsations. It is assumed that Pc5 pulsations observed after the negative IMF B _z front are related to the development of surface waves at the magnetopause as a result of impulsive reconnection of field lines.