AsianScientist (Apr. 17, 2017) – Magnetic storms recorded in two ancient Asian texts have given researchers the ability to reconstruct a chronology of past astronomical events. Their findings appeared in the journal Space Weather.
Ice cores and ancient sediments can be gleaned for clues to weather and climate in the past. But astronomical phenomena—such as solar flares or auroras—at best leave only faint environmental traces lacking in specificity. So how can we accurately track ancient astronomical events?
Now in a collaborative effort between the arts and sciences, researchers at Kyoto University and Japan’s National Institute of Polar Research (NIPR) and National Institute of Japanese Literature (NIJL) have used historical documents to garner better insight into the patterns of past solar events.
They used auroral sightings recorded in Meigetsuki (“The Record of the Clear Moon,” ca 1180-1241) by Fujiwara no Teika of Japan, and a sunspot documented in Song Shi (“History of Song,” commissioned 1343) from China. Such sunspots are an indication of intense magnetic activity on the sun, including solar flares.
“An early Japanese record of prolonged auroras, that is, auroras that persisted for two or more nights within one week, was documented 21-23 February 1204 in Meigetsuki,” said lead researcher Ryuho Kataoka of NIPR. “At the same time in Song Shi, a large sunspot was recorded on the 21st.”
The researchers continued their investigation by looking further into Song Shi to see if there were additional indications of auroras between the years 900-1200.
“We found about ten incidents of prolonged auroras during this period,” added Kyoto University historian Hisashi Hayakawa. “When these dates were compared with radiocarbon data from tree rings, we noted decreased levels of carbon-14—indicating increased levels of solar activity—at these same points.”
The team was also able to discern that auroras were more prevalent in the maximal phase of solar cycles rather than the minimum, and that during the sun’s least active cycle (1010-1050) no auroras were observed.
“Combining literature, tree ring dating, and space observation, we have uncovered clear patterns in solar activity and astronomical events,” said Kyoto University space scientist Hiroaki Isobe.
“In the present day, large solar storms can significantly disrupt power grids and satellites. We are ever more susceptible to solar events, and the insight gained through historical documents allows us to better predict and prepare for the future.”
The article can be found at: Kataoka et al. (2017) Historical Space Weather Monitoring of Prolonged Aurora Activities in Japan and in China.
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Source: Kyoto University.
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