6:15 PM - 7:30 PM
[U06-P14] Cosmic-ray physics as a seamless science
Keywords:cosmic ray, the sun, earth's atmosphere, hadron interaction, ion-induced nucleation
Three subjects in the cosmic-ray study are (a) mechanism of acceleration and production, (b) nature of cosmic-ray particles themselves and (c) propagation and relation to the sun and the earth in neighboring environment. Here, two detailed topics connected from the space to the solar-terrestrial environment are introduced.
The frequency of cosmic-rays around the highest energy is less than 1 particle/km2/year. Good statistical detection with such low frequency needs an extensive observation site. In the measurements of primary cosmic ray energy and nuclear species, florescence detection of air showers originated by cosmic rays and extended sampling detection of air shower particles at the ground are used together with simulations. However, particularly for ultra-high energy regions, hadron interaction models used in simulations have not yet verified and this uncertainty gives large systematic errors for determination of cosmic ray energy and species of nuclei. We are carrying out a verification experiment (LHCf collaboration) at LHC, which is a particle accelerator with the highest energy in the world. We have obtained good results up to the energy of 1017 eV equivalent with proton-proton collisions. In order to apply to the real air shower, collision experiments of proton-light nucleus (nitrogen, oxygen, etc.) and light nucleus-light nucleus to iron nucleus are needed.
Cosmic-ray particles entering the earth initiate nuclear interactions with atmospheric atomic nuclei and produce many secondary particles. These secondary cosmic-rays create atmospheric ions according to their ionization ability. It is considered that these ions promote the production and growth of aerosol particles, which become cloud condensation nuclei in the atmosphere. We are trying to verify the correlation between the time variations in the cosmic-ray intensity measured by neutron monitors at the ground and the earth’s low-altitude cloud cover, by a chamber experiment with artificial radiation sources.
Cosmic rays reach the earth surface from the space far away through the heliosphere and the earth’s atmosphere, and interact with each region. It is necessary to consider such broad regions connecting seamlessly.
We have conducted the study on elementary process on cosmic-ray interactions with earth’s atmosphere and verification of its relation to global climate, and would like to clarify the seamless process through the cosmic-rays. In this talk, we introduce the details of these studies.