Development of four magnetic storms in February 1972

Four magnetic storms were observed in February 1972, with instruments on the Explorer 45 satellite in the evening quadrant of the inner magnetosphere. The magnitude of the storms ranged from small, D_st ? ?40 γ, to moderate, D_st ? ?80 γ. During the development of the storms several substorms occurred. At the beginning of the substorms there was evidence of a partial ring current above L = 5. After the expansion phase of several substorms there was evidence of enhancement of a partial ring below L = 5. Distortions of the field in the east-west direction were observed, in conjunction with substorm expansions, that can be interpreted as due to field aligned currents flowing from the ionosphere. A substantial symmetric ring current, at L～4, developed during the largest storm. Very little additional ring current was contributed by the smallest storm. Relations between the magnetosphere inflation and ring current protons, plasmaspheric hiss, and ULF waves also measured on Explorer 45 were noted.