Solar activity and geomagnetic storms: The first 40 years

This article is the first of a series of three that traces the evolution of our understanding of the relationship between solar and geomagnetic activity from the mid‐19th century to the present era. The origin of solar‐terrestrial physics is generally traced to Sabine's recognition in 1852 that geomagnetic activity paralleled the recently discovered sunspot cycle. Perhaps less well appreciated is the slow and uneven pace of progress since then in forging definite links between solar and geomagnetic activity. Thus 50 years after the initial excitement attending Sabine's discovery, the role of the Sun as the fundamental cause of magnetic storms was a matter of contention, and nearly a century would pass before statistics were sufficient to make a convincing case for an association between large solar flares and severe storms.