cause of the $^{14}$C variation.

Miyake et al. (2012) argued that neither a supernova (SN) nor a solar or stellar flare could be the cause for this event, because there is no Chinese observation of a historic SN known around that time and because solar and stellar flares are neither strong nor hard enough for the AD 774/5 variation in $^{14}$C and possibly also $^{10}$Be.

Allen (2012) suggested that a certain report in the Ang- lo-Saxon Chronicle ([*This year also appeared in the heavens a red crucifix, after sunset*]{}), presumably for AD 774, may be an absorbed SN; however, a SN cannot be observed as resolved or extended object ([*cross*]{}). The sightings of a [*red cross*]{} or [*crucifix*]{} can easily be explained as halo display with horizontal arc and vertical pillar, possibly also with sun-dogs (parhelion) or moon-dogs (paraselene), the frequent reports about them in medieval times can be explained by the fact that the Christian monks (who reported them) thought at that time that the sighting of a cross in the sky (or heaven) would indicate the presumable return of Jesus or their Messiah, see Neuhäuser & Neuhäuser (2014). It was also shown that the above [*red cross*]{} was 