Younger Dryas solar flare

[Amped]

http://www.spacedail..._Earth_999.html

The two largest 14C spurts to occur in the 4000 year Cariaco record occurred in particular during the first three centuries of this early YD period.

The Cariaco Basin varve chronology dated these events at 12,837 years BP and 12,639 years BP.

Interestingly, they were separated by 198 +/- 9 years, or nine Hale solar cycle periods.

This interval also matched the 200-year de Vries solar cycle period which is believed to be one of the most prominent of the Sun's solar cycle periods.

This was the smoking gun that indicated that these spurts very likely had a solar cause.

And, there were two other notable 14C spurts of lesser magnitude that preceded the 12,837 years BP event, each separated from the other by three Hale solar cycle periods.

The radiocarbon increase of the two largest 14C spurts was comparable to that produced by a SPE at least 125 times stronger than the hard spectrum SPE that occurred in February 1956.

Extrapolating upward from that event, LaViolette estimates that the 12,837 years BP extinction level SPE would have delivered over a two day period a radiation dose of from 3 to more than 6 Sieverts, lethal dose (LD-100) for most mammals being in the range of 3 - 8 Sieverts. Hence it could have been a principal cause of the final termination of the Pleistocene megafauna and even of several genera of smaller mammals and birds.

Actual article is much longer

[aslkahuna]

That would be one hell of a flare to cause that much of a Ground Level Effect. A nearby Supernova would also fill the bill.

Steve