solar event. What event was that?
The August 1972 event to which you refer was a major solar flare, one of the best-observed flares in history. Very intense flares of this type occur typically once in every solar cycle (a similar event occurred in 1989). It was almost certainly accompanied by a coronal mass ejection similar to those now frequenty observed by SOHO. However, coronal mass ejections had not yet been discovered in 1972, mainly because the equipment necessary to observe them (space-based coronagraphs) had not been sufficiently well-developed at the time. (Well, HAO’s Mark III coronagraph can see CMEs from the Mauna Loa observatory in Hawaii, but orbiting spacecraft saw them first.) This event was of more than usual importance because it was in a suitable location on the Sun to cause severe geomagnetic effects — as was the 1989 event. Interestingly, it occurred between manned flights to the Moon in April and December 1972 (Apollo 16 and Apollo 17); had it occurred during either of these flights, the dose of
