▶ Date: 2022.03.17(THU)

▶ Time: 4:30pm ~ 5:30pm

▶ Speaker: Prof. Tatsuhiko Sato(Osaka University / Japan Atomic Energy Agency)

▶ Title: Radiation environment in space and recent progresses on space weather research for cosmic-ray dosimetry

▶ Abstract:

The radiation environment in space is a complex mixture of particles of solar and galactic origin with a broad range of energies. For astronaut dose estimation, three sources must be considered, namely, galactic cosmic rays (GCR), trapped particles (TP), and solar energetic particles (SEP). GCR enters the heliosphere continuously from all direction, and they are modulated by the interplanetary magnetic field produced by the charged particles emitted continuously by the Sun, the so-called ‘solar wind’. Thus, their fluxes gradually change with the solar activity, which has a period of approximately 11 years. TP is trapped in the Earth’s magnetic fields as a result of interaction of GCR and SEP with the Earth’s magnetic field and the atmosphere. Thus, they contribute to the astronaut doses only for the Earth orbit missions. SEP is emitted from the Sun’s surface due to the coronal mass ejection (CME) over the course of hours or days. By contrast to GCR and TP, the astronaut dose due to SEP exposure during a space mission is hardly expectable because the occurrence of a large CME is unpredictable by the current space weather research. Thus, the worst-case scenarios are generally considered in mission design. More details about the radiation environment in space will be presented at the seminar, together with the recent progresses on the space weather research for nowcasting and forecasting the astronaut doses due to SEP exposure.

A brief explanation of our developing code PHITS, which is a Monte Carlo particle transport simulation code widely used in variety of research fields including cosmic-ray dosimetry, will be also presented.