{"id":2301,"date":"2026-04-10T04:11:09","date_gmt":"2026-04-10T04:11:09","guid":{"rendered":"https:\/\/www.europesays.com\/japan\/2301\/"},"modified":"2026-04-10T04:11:09","modified_gmt":"2026-04-10T04:11:09","slug":"medieval-japanese-poetry-and-buried-trees-help-elucidate-volatile-space-weather","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/japan\/2301\/","title":{"rendered":"Medieval Japanese poetry and buried trees help elucidate volatile space weather"},"content":{"rendered":"

\"Medieval<\/p>\n

Red aurora over Engaru, Hokkaido, Japan. Credit: Tomohiro M. Nakayama<\/p>\n

On Earth, extreme solar activity often appears as beautiful, benign auroras. But venturing beyond the safety of the Earth’s magnetic field, one faces the full brunt of a temperamental star that can suddenly erupt with flares and coronal mass ejections.<\/p>\n

These outbursts occasionally trigger so-called solar proton events (SPEs), in which high-energy particles are flung towards Earth at up to 90% of the speed of light.<\/p>\n

In 1972, a string of SPEs<\/a> occurred between the Apollo 16 and 17 moon missions\u2014had these coincided with either expedition, the astronauts would have been helplessly exposed to deadly particle radiation. As we return to the moon, understanding these sporadic events is becoming more urgent.<\/p>\n

Now, researchers from the Okinawa Institute of Science and Technology (OIST) have shown a new approach for detecting historical SPEs, where they use medieval records to guide ultra-precise carbon-14 measurements of buried asunaro trees in Northern Japan.<\/p>\n

Using this combined approach, the physicists have identified and dated an SPE to a period between winter 1200 to spring 1201 CE in the medieval period, when solar activity was extremely high. Their findings were published in the Proceedings of the Japan Academy, Series B<\/a>.<\/p>\n

Professor Hiroko Miyahara from the OIST Solar-Terrestrial Environment and Climate Unit explains, “Previous studies on historical SPEs have focused on rare, extremely powerful events. Our paper provides a basis for detecting sub-extreme SPEs\u2014events that occur more frequently and are around 10\u201330% of the size of the most extreme cases, but still hazardous.<\/p>\n

“Sub-extreme SPEs are more challenging to detect, but our method now allows us to efficiently identify them and better understand the conditions under which they are more likely to occur.”<\/p>\n

\"Medieval<\/p>\n

Until last week, Apollo 17 was the last time humans left low-earth orbit to visit the moon. Several solar proton events occurred in the same year as Apollo 16 and 17; had these coincided, the astronauts would have been exposed to deadly radiation without protection. Credit: NASA (Public domain)<\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tRed lights in the northern sky<\/p>\n

Most high-energy protons from SPEs are deflected by Earth’s magnetic field. However, near the poles, where the geomagnetic field lines are open to space, or during particularly strong events, some particles can get through and collide with atmospheric gases. This forms carbon-14 compounds that circulate globally through the atmosphere and are incorporated into organic materials.<\/p>\n

By measuring the carbon-14 content in preserved organic material, such as buried trees, researchers can identify fluctuations in solar activity over the last 10,000 years. With ultra-precise measurements<\/a>\u2014which the researchers previously developed over a decade-long process\u2014smaller fluctuations that are impossible to detect with conventional methods can now be seen, allowing detection of sub-extreme SPEs.<\/p>\n

However, because the ultra-precise method is time-consuming, the team needed to first know when and where to look for evidence of past solar weather events. In the present study, the first clue came from Meigetsuki, the diary of the influential Japanese courtier and poet, Fujiwara no Teika (1162\u20131241), who witnessed “red lights in the northern sky over Kyoto” in February 1204 CE.<\/p>\n

While SPEs do not themselves cause aurora, they often accompany space weather that does, providing a target period for the researchers to investigate. They then measured the carbon-14 content of asunaro wood unearthed in the northern Aomori Prefecture and found carbon-14 spikes indicative of a sub-extreme SPE.<\/p>\n

\n Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights.
\n Sign up for our free newsletter<\/a> and get updates on breakthroughs,
\n innovations, and research that matter\u2014daily or weekly.\n <\/p>\n

Together with dendroclimatic studies<\/a>\u2014that is, a dating method based on comparing patterns of tree-ring growth associated with regional climate\u2014the researchers placed this specific event sometime between winter 1200 CE and spring 1201 CE, a period during which a red, low-latitude aurora had been seen in China.<\/p>\n

\"Medieval<\/p>\n

An Edo-period illustration of Fujiwara no Teika. Credit: Kikuchi Yosai<\/p>\n

\"Medieval<\/p>\n

A hand-copied version of Fujiwara no Teika’s diary, Meigetsuki, from the Edo period. The page shown includes references to “red lights in the northern sky” on the right-hand side. Credit: National Archives of Japan<\/p>\n

\"Medieval<\/p>\n

The asunaro cypress tree samples, unearthed at Shimokita Peninsula in northern Aomori Prefecture. The sample is provided by Tohoku University. Credit: Hiroko Miyahara\/OIST<\/p>\n

\"Medieval<\/p>\n

Reconstructed solar cycles based on carbon-14 records, relative to baseline activity level at y=0, overlaid with historical records: orange circles denote the timing of aurora sightings, blue and red stars denote prolonged aurora events like those described in Meigetsuki, and black diamonds indicate the emergence of large sunspots. Credit: Miyahara et al., 2026<\/p>\n

“The high-precision data not only allowed us to accurately date sub-extreme solar proton events, but it also lets us clearly reconstruct the solar cycles of the period,” adds Miyahara.<\/p>\n

“Today, the sun’s activity fluctuates over eleven-year-long cycles, but we’ve found that the cycle was just seven to eight years long back then, indicating a very active sun. The SPE we have dated occurred at the peak of one of these cycles.”<\/p>\n

This study helps close gaps in the historical record of solar activity, thereby improving our understanding of unpredictable and hazardous events like SPEs. But as Miyahara emphasizes, precise carbon-14 measurements must be combined with other approaches.<\/p>\n

“Historical literature provides a candidate time window, and dendroclimatology enables direct intercomparison between detected SPE and reports of sunspots and auroras recorded in literature. Integrated approaches like these are necessary to accurately reconstruct past solar activity, helping us better understand the characteristics of extreme space weather,” concludes Miyahara.<\/p>\n

“For example, while the SPE we found occurred near the peak of the solar cycle, some of the prolonged low-latitude aurora recorded in the literature seems to fall near the minimum of our reconstructed solar cycle. This is unexpected, and we’re excited to look further into what solar conditions could cause this.”<\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\tMore information\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

Extremely Active Sun from 1190 to 1220 in the Medieval Period: Intercomparison of Historical Records and Tree-ring Carbon-14, Proceedings of the Japan Academy Series B (2026). DOI: 10.2183\/pjab.102.011<\/a><\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t\t\tProvided by
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tOkinawa Institute of Science and Technology<\/a>
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t\tCitation:
\n\t\t\t\t\t\t\t\t\t\t\t\tMedieval Japanese poetry and buried trees help elucidate volatile space weather (2026, April 9)
\n\t\t\t\t\t\t\t\t\t\t\t\tretrieved 10 April 2026
\n\t\t\t\t\t\t\t\t\t\t\t\tfrom https:\/\/phys.org\/news\/2026-04-medieval-japanese-poetry-trees-elucidate.html\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
\n\t\t\t\t\t\t\t\t\t\t\t part may be reproduced without the written permission. The content is provided for information purposes only.\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n","protected":false},"excerpt":{"rendered":"Red aurora over Engaru, Hokkaido, Japan. Credit: Tomohiro M. Nakayama On Earth, extreme solar activity often appears as…\n","protected":false},"author":2,"featured_media":2302,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[8,17,1860,1861,1859,1856,1124,1857,907,1858],"class_list":{"0":"post-2301","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-japan","8":"tag-japan","9":"tag-japanese","10":"tag-materials","11":"tag-nanotech","12":"tag-physics","13":"tag-physics-news","14":"tag-science","15":"tag-science-news","16":"tag-technology","17":"tag-technology-news"},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts\/2301","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/comments?post=2301"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts\/2301\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/media\/2302"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/media?parent=2301"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/categories?post=2301"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/tags?post=2301"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}