The next decade should see rapid progress in our understanding of the nature and cause of the transitory changes in the geomagnetic field known as magnetic storms. We also expect to improve our understanding of related phenomena such as the aurora, cosmic ray time changes, and ionospheric storms.The reason for this present optimistic point of view is the arrival of the space age, through which an added dimension has become accessible. Rocketand satellite-borne magnetometers and counters are already extending the measurement of geomagnetic changes and radiation to regions thousands of kilometers above the earth, thereby augmenting human knowledge by providing directly measured data on magnetic storms and auroras in their natural surroundings.It may be of interest here to recall briefly the history of the study of magnetic storms. Hiorter in 1741 is usually credited with the discovery that the geomagnetic field undergoes occasional changes in intensity on nights of aurora. Even earlier the British astronomer Edmund Halley had ascribed auroras to "magnetic effiuvia" constrained to move along the direction of the lines of force of the geomagnetic field within the atmosphere. In view of the very early date, this was a most remarkable exhibition of scientific insight. By about the middle of the 19th century the relation-