A great magnetic storm commenced on April 17, 1965. Explorer 26 carried a moving magnetic observatory through the inner magnetosphere, L = 2 to L = 6, many times during the development and recovery of the storm. The main phase was asymmetrical and was apparently caused by the rapid growth of a large body of charged particles in the evening and late afternoon quadrants. The recovery phase was more symmetrical and appears to be due to inflation of the magnetosphere by a belt, centered at L = 3.5 on the equator, of charged particles encircling the earth. The decay time constant of this belt was about 4 days.
L. J. Cahill (Sat,) studied this question.