At https://phys.org/print410606948.html … researchers from Kyoto University and Japan's National Institute of Solar Research have used historical records to garner a better insight into the patterns of past solar events and their impact on the earth (such as intense aurorae). Japanese and Chinese documents (no mention of Korean examples of a similar nature) have enabled them to reconstruct a chronology. The study is published in 'Space Weather' (April 2017). For example, an early Japanese record of aurora sightings describes a prolonged event in AD1204. The document recorded both aurora and a prominent sun spot. They found ten such incidents between 900 and 1200AD and when compared with the C14 record in tree rings they noted a decrease – indicating increased levels of solar activity (at the same points in time). Surprisingly, the least active period of solar activity was between 1010 and 1050 – a period of time that includes a major event of some kind, pinpointed in tree rings. It seems that solar activity has been ruled out by this study – so what else was going in 1040 to cause a huge sea flood in the western approaches?
For more information go to DOI:10.1002/2016SW001493 (or direct from Kyoto University)