Fusa Miyake

Scientific career

Fusa Miyake gained her doctorate from Nagoya University in 2013 and was then appointed as an assistant professor. In 2017 she was promoted to associate professor in the Division for Cosmic Ray Research within the Space-Earth Environmental Research Division.

Her doctoral research identified events in the wood of long-lived Japanese cedar trees, now called Miyake events, where there are sudden increases in cosmogenic isotopes such as radioactive carbon isotope ¹⁴
C, ¹⁰
Be and ³⁶
Cl produced by cosmic rays originating from the Sun when large solar flares or eruptions occur. These isotopes can be detected in materials such as tree-rings and ice cores. Although the event was initially proposed to be a signature of an unidentified supernova, it was soon proven to be the discovery of an extreme solar particle event and confirmed independently. As an example, measurements can utilised the carbon in the polymer cellulose extracted from tree-rings formed in individual years to measure abundance of the isotope ¹⁴
C using accelerator mass spectrometry. Measuring these isotopes in materials that have been independently dated allow the events to be dated with precision. This gives information about the Sun's long-term activity. She identified an event in 775 during her doctoral work, and along with colleagues, has subsequently identified events centred on 993-4 and also 660 and 5480 BCE. By 2023, 6 Miyake events had been identified.

Her subsequent research with worldwide collaborators, and that of other researchers, has suggested that the source of the radiation causing Miyake events is more complicated than from single solar events. Some may be from multiple solar flares, influenced by tree physiology or by interactions of high energy particles with the Earth's magnetic field.