Flares associated with the 1960 November event and the flare nimbus phenomenon

The "flare nimbus" is a large-scale, dark, expanding halo sometimes faintly seen in Hα observations of major flares. As a paper by McKenna-Lawlor notes, it has not been so fashionable nowadays (i.e., the 21st century) to observe this sort of thing, but on the other hand her interpretation is quite modern: it's due to a large-scale restructuring of the magnetic field. The nimbus would then be an Hα consequence of the ``dimming'' signature. Other interpretations might also exist, e.g. the trapped particles shown in this cartoon. Or, the pictures might be combined, since major eruptive flares have both dimmings and particles.

      Note that this cartoon was added to the Archive exactly half a century after it was first published! See the McKenna-Lawlor paper for the modern history.