Abstract: Inter. Conf. on Alpine and Polar Microbiology, Inn

Abstract: This paper analyses atmospheric ionizing radiations induced by Galactic and Solar Cosmic Rays (GCR and SCR, respectively) thanks to continuous measurements of neutron spectrum operated in high-altitude stations. Analyses are reinforced using GCR and SCR models, and extensive air shower descriptions
based on nuclear transport simulations. First analyses were focused on neutron fluxes as function of altitude. Secondly, atmospheric ionizing radiation impacts on biological doses during quiet period and extreme solar events are presented. On the basis of the relevant comparisons conducted for ambient dose equivalent
during quiet solar activity, but also for the comic ray variations calculated and recorded on neutron monitor (NM) during Ground Level Enhancement (GLE) event. GLE 5 model was applied to London ↔ New-york flight dose calculations. All of these results show that dose values vary drastically, on the one hand with the route path (latitude, longitude altitude), on the other hand with the phasing of the solar event. Specific case of Antarctica is discussed because it combines both the high altitude and the very low magnetic field. Analyses show that ionizing radiation in Antarctica environment can be a problematic from the point of view of the human dose, which exerts classical recommendations established for public. This highlights the importance of monitoring atmospheric ionizing radiation, more particularly extreme solar events, then to develop semi-empirical and particle transport method for reliable calculation of dose levels.

Abstract: Several applications exist that calculate cosmic-ray-induced particle (CRIP) spectra as a function of the altitude in the atmosphere. In general, the Earth's magnetic field is only used to modulate the primary cosmic radiation that arrives at the top of the atmosphere, but it can also modulate low-energy charged particles at flight altitudes. The effects of the Earth's magnetic field on the angular distributions of CRIP transport in the atmosphere should be quantified, because it furnishes important data for the development of applications for aircrew radiation protection, onboard dosimetry and the simulation of irradiation of sensitive equipment and particle detector systems used at ground level, flight and atmospheric balloon altitudes. In this work we calculate the angular distribution of the cosmic-ray-induced particles (CRIP) for altitudes from ground level up to 80?km using an application based on Geant4 developed in previous works. In order to quantify the effects of the Earth's magnetic field (EMF) on the angular distribution of the CRIP, the calculations were carried out both including the EMF in the South Atlantic Magnetic region and omitting it. A part of these results were compared with analytical calculations of the ratio between the mean free path of the primary particles from the cosmic radiation and the deflection radii at different altitudes in the atmosphere. The albedos of neutrons and protons at 80?km were estimated and compared with the QARM and ATMORAD codes, which ignore the Earth's magnetic field.