Tau.Neutrino said:
Extreme Miyake radiation events captured in tree rings stump scientists
The most intense solar storm in recorded history, known as the Carrington event, damaged nascent power and communication networks in the Victorian era.
But Earth has been hit by radiation levels that were up to 100 times greater than this, according to a new study of spikes in radiocarbon stored in tree rings.
more…
> Along with solar storms, other galactic phenomena including gamma-ray bursts, supernova explosions and blasts from nearby neutron stars have been put forward as options.
> Data from the study showed that these mysterious radiation storms occurred roughly once in 1,000 years and happened right across the solar cycle, not just solar maximum. Many of the spikes lasted longer than normal solar storms. At least one event in 663 BC lasted up to three years, and another in 5480 BC built up across a decade.
> Dr Pope’s best guess is that the longer duration spikes may come from a series of outbursts from the Sun. Not just one solar flare, but recurrent solar flares going off again and again.
They seem to have missed the possibility that the radiation was released in volcanic eruptions. Volcanic eruptions can release a lot of radiation. That at least would explain the durations observed, and the lack of an aurora.