On the theoretical side, we numerically simulate:

• (1) Changes in the chemical composition of the stratosphere induced by high-energy photons and/or particles emitted from explosive astronomical phenomena, such as solar proton events and galactic supernovae, and
• (2) Explosive nucleosynthesis, including that of elements heavier than iron, arising in the environment of core-collapse supernova explosions.

　Subjects (1) and (2) themselves are very important in solar-terrestrial research and nuclear astrophysics, respectively; furthermore, they are intended to be coupled with experimental studies. On the experimental side, we analyze the ice cores drilled at the Dome Fuji station in Antarctica in collaboration with the National Institute of Polar Research, Tokyo. These ice cores correspond to time capsules of the past. In particular, the ice cores obtained at Dome Fuji are known to be unique because they contain much more information on conditions in the stratosphere than any other cores recovered from other locations in either hemisphere. This means that astronomical information can be obtained using the Dome Fuji ice cores. Accordingly, we measure:

• (3) Variations in the ion concentrations in the ice cores, in order to seek the proxy of past solar activity and the footprints of supernovae in our galaxy, and
• (4) Variations in the water isotopes (¹⁸O and ²H) in the ice cores, in order to study past atmospheric temperature variability on the earth.

　Here, the basis for item (4) is already established in glaciology. By comparing the experimental results for items (3) and (4), we aim to understand the relationship between solar activity and climate change in the past on the millennium scale. Theoretical studies related to items (1) and (2) will provide a background for distinguishing the characteristics of the astronomical events that can be recorded in the ice cores.