This paper investigates past and possible future magnetic storm intensifications. As part of this work, a dataset is developed of the most intense and second most intense storms for each of the past eleven solar cycles (1902-2016) – augmenting a traditional dataset that only covers the past six solar cycles (1957-2016) with recently published intensities for several magnetic superstorms and with new storm intensity estimates, reported here and derived from historical magnetic observatory records. These data are analyzed using statistical methods that provide estimates of the probability of future magnetic superstorms.
The study finds that a storm as intense as that of March 1989, which caused widespread disruption of technological systems and an electricity blackout in Qu ́ebec, Canada, is predicted to occur, on average, about every four solar cycles. This is twice as often as estimated using only the traditional shorter dataset. A once- per-century storm is estimated to be more substantially more intense than that of March 1989.