Nagoya University
Institute for Advanced Research / Institute for Space–Earth Environmental Research (ISEE)
YLC Designated Assistant Professor

Research Areas:Informatics
Humanities & Social Sciences
Natural Science

Research fields

Solar-Terrestrial Physics
Space Weather
Environmental History

Research Interests

Solar-Terrestrial Environment
Space Weather
Environmental History
Solar Physics

Professional Memberships

Astronomical Society of Japan
Society of Geomagnetism and Earth, Planetary and Space Sciences

Main research topics

The extreme solar storms seriously affect the technological infrastructure of our civilisation. It is known that occurrence of the greatest solar storms in the observational history can be catastrophic to the modern civilisation. Their magnitude has been partially evaluated with the Dst index from 1957 onward. However, historical records and proxy evidence has shown some possible cases with far greater storms than what are known to the modern scientific observations.

This project aims at analysing and quantifying such solar storms using past analog records and historical documents for sunspots, geomagnetism, and auroral visibility, extending their time series to three millennia. This project aims at conducting their case studies to help visualisation of their upper limits, occurrence frequencies, and background mechanism and constrain the existing model studies for the extreme solar storms.

Therefore, this project aims at consulting these analog records and historical documents over the world. This project plans collaborations with specialists in each relevant field beyond the borders and research fields. This collaborative project will allow us to extend the chronology of the solar storms to three millennia, on the basis of original records for such solar storms all over the world.

Geographical distribution of the auroral visibility during the extreme solar storm in September 1859 (Hayakawa et al., 2020, Earth Planets & Space, 72, 122).


Representative papers

Hayakawa, H., Ebihara, Y., Willis, D. M., Toriumi, S., Iju, T., Hattori, K., Wild, M. N., Oliveira, D. M., Ermolli, I., Ribeiro, J. R., Correia, A. P., Ribeiro, A. I., Knipp, D. J. (2019) Temporal and Spatial Evolutions of a Large Sunspot Group and Great Auroral Storms around the Carrington Event in 1859, Space Weather, 17, 1553– 1569. DOI: 10.1029/2019SW002269.

Hayakawa, H., Mitsuma, Y., Ebihara, Y., Miyake, F. (2019) The Earliest Candidates of Auroral Observations in Assyrian Astrological Reports: Insights on Solar Activity around 660 BCE, The Astrophysical Journal Letters, 884, L18. DOI: 10.3847/2041-8213/ab42e4

Research URL

researchmap https://researchmap.jp/hisashi.hayakawa

Global issues to be solved through this project

Investigations and quantitative reconstructions of the extreme solar storms in the last 3 millennia on the basis of historical archival records

This project aims at investigating and quantifying extreme solar storms over the last three millennia. It is known that solar storms occur more frequently under enhanced solar activity. Among them, the most extreme solar storms occur only infrequently but significantly affect the modern technological infrastructure. Accordingly, these solar storms can be a new natural disaster for the modern civilisation and have required worldwide researches on their understanding, countermeasures, and disaster mitigations. For this global issue, this project aims at extending the scientific chronology to three millennia, using analog records and historical documents for sunspots, aurorae, and geomagnetism. This project also proposes case studies and comprehensive analyses for historical solar storms on the “observational” basis.