One of the strongest known solar storms blasted Earth in 660 B.C.
Traces left in ice cores and tree rings allowed researchers to estimate the storm’s power
BLASTS FROM THE PAST Swift, powerful bursts of charged particles emitted by the sun can be strong enough to breach Earth’s magnetosphere (blue bubble in illustration). To see how common such emissions have been in Earth’s past, scientists look for telltale data in tree rings and ice cores.
NASA