H Hayakawa*
*Graduate School of Letters, Osaka University, Toyonaka, 5600043, Japan


Figure 1: The earliest record of auroral candidate in Japanese historical documents (courtesy: the National Archives of Japan).

In this presentation, we show the historical geomagnetic storms before the Carrington event indirectly observed as low latitude aurorae in Japan and buried in historical documents. The recent solar eruptions evidently show that the Sun can cause severe magnetic storms by their flares and CMEs even in its declining phase of the 11-year cycle activity. On our Sun, however, the data currently we have is not necessarily abundant. We have sunspot observations for 400 years since early 17 th century (Owens, 2013) and flare observations for 160 years since the Carrington event in 1859 (e.g. Carrington, 1859; Tsurutani et al., 2003). The latter is also known to have caused one of the largest known magnetic storms in observational history (Tsurutani et al., 2003; Cliver & Dietrich, 2013). However, the observational data does not necessarily let us know how frequent or how large magnetic storms can be caused by solar flares, due to their relatively short coverage.

Historical documents however may overcome this difficulty. In the Carrington event, for example, we have witnessed great auroral displays in low latitude areas (Cliver & Dietrich, 2013). They were also the case in Japan and other East Asian countries as well (Hayakawa et al., 2016b). We therefore show how auroral displays were recorded in Carrington event and can be compared with the known magnetic observations in Tsurutani et al. (2003). The result shows that we can scale the magnitude of magnetic storms taken place before the Carrington event with equatorward extension of auroral displays. Therefore, we also show and examine the three variants of Japanese auroral drawings that are associated with a great magnetic storm previously mentioned by Willis et al. (1996) and Nakazawa et al. (2004). We then show survey results of auroral candidates in Rikkokushi, six Japanese Official Histories from the early 7th century to 887 to excavate previously unknown magnetic storms such as those shown in Figure 1 (see, Hayakawa et al., 2017c). We then compare them with the lunar phase to estimate how reliable they are, and compare these records with the contemporary TSI data from radioisotope data (Steinhilber et al., 2007) and sunspot records in contemporary China (Tamazawa et al., 2017). We also identify the observational sites to review possible auroral expansion to the magnetic equator. Our result shows not only candidates of magnetic storms captured in ancient Japanese historical records, but also the large absence of auroral records in late 7 th century corresponding with the candidate of grand minimum (640-710; Usoskin et al., 2007), a similar tendency with the distributions of sunspot records in contemporary China.

We are currently constructing the database of historical observations of aurorae and sunspots to review pre-telescopic solar activity based on our relevant papers (Hayakawa et al., 2015, 2016a, 2016c, 2017c, 2017d; Kawamura et al., 2016; Tamazawa et al., 2017). Considering that historical documents allow us to trace back auroral records up until 567BC (Stephenson et al., 2004; Hayakawa et al., 2016c) and auroral drawings up until 771/772 (Hayakawa et al., 2017b), we believe that the database on such data buried in historical documents will cast new lights on the researches of the solar-terrestrial environment.


We acknowledge the support of Kyoto University’s Supporting Program for the Interaction-based Initiative Team Studies “Integrated study on human in space” (PI: H. Isobe), the Interdisciplinary Research Idea contest 2014 by the Center for the Promotion of Interdisciplinary Education and Research, the “UCHUGAKU” project of the Unit of Synergetic Studies for Space, the Exploratory and Mission Research Projects of the Research Institute for Sustainable Humanosphere (PI: H. Isobe) and SPIRITS 2017 (PI: Y. Kano) of Kyoto University, and the Center for the Promotion of Integrated Sciences (CPIS) of SOKENDAI. This work was also encouraged by a Grant-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology of Japan, Grant Number JP15H05816 (PI: S. Yoden), JP15H03732 (PI: Y. Ebihara), JP16H03955 (PI: K. Shibata), and JP15H05815 (PI: Y. Miyoshi), and Grant-in-Aid for JSPS Research Fellow JP17J06954 (PI: H. Hayakawa). H. H. thanks the National Archive of Japan and the Hirosaki City Library for providing relevant manuscripts.


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