# Simulation and Evaluation of the Radiation Dose Deposited in Human Tissues by Atmospheric Neutrons
## 1 Introduction  
The atmospheric air showers are initiated by high-energy primary cosmic rays that enter the atmosphere isotropically from outer space, producing a large number of secondaries particles in a serie of successive collisions with target nuclei of the atmospheric constituents [1]. The primary cosmic rays which consists predominantly of protons, alpha particles and heavier nuclei are influenced by the galactic, the interplanetary, the magnetospheric and the geomagnetic magnetic fields while approaching the Earth [2].  
In addition, the incoming cosmic rays with energies below about 20 GeV are modulated by the interplanetary magnetic field which is embedded in the solar wind [3], the expanding magnetized plasma generated by the Sun, which decelerates and partially excludes the lower energy cosmic rays from the inner solar system. There is a significant anticorrelation between solar activity and the intensity of the cosmic rays with the energies already mentioned.  
Atmospheric neutrons are secondary particles resulting from interactions of primaries with nuclei of air constituents. It is useful to distinguish low-energy neutrons with energies less than about 10 MeV from high-energy neutrons. Low-energy neutrons are mostlyevaporation products of excited nuclei and manifest an isotropic angular distribution. High-energy neutrons can be produced by hadronic collisions but also in charge exchange reactions of leading particles at very high energies, the angular distribution of high energy neutrons is anisotropic [2]. In addition, when high-energy particles collide with the atoms in the aircraft material, producing a local shower of particles, including electrons, lighter ions, gamma rays, and neutrons that are dangerous to human health [4].  
Because the neutrons are produced by charged particles they inherit and also exhibit both latitude and longitude effects. Furthermore the flux of the low-energy neutron component is modulated by the solar cycle; in addition, strong solar flares may cause significant neutron fluxes in the atmosphere [2], sporadic enhancements of solar cosmic ray fluxes are also caused by coronal mass ejection, in these events the particles are accelerated to energies of hundreds of MeV up to several GeV [5; 6].  
The secondary energetic particles interacting with the human body may potentially cause an increase in cancer risk as the dose equivalent exposure increases, particularly in passengers and flight crew [7]. High RD may cause the breaks, potentially lethal to the cell by damaging the DNA strands, while low RD of ionizing radiations seems to have carcinogenic effects, even after years or decades, both in the exposed individuals and in subsequent generations [8]. The atmospheric neutron component of this complex radiation field, in particular, holds special interest in the cancer research community. At aircraft altitude (flight level around 10 km) of the total radiation dose deposited by secondary particles, the contribution of neutrons is around 40% [9].  
The potential negative effect of atmospheric neutrons on human health is the motivation to carry out the present work, in this, we developed a numerical simulation using Geant4 software, with which, we calculated the radiation dose (RD) deposited by atmospheric neutrons in various tissues of the human body as function of the fluxes of these particles for various altitudes and latitudes; however, in all these geographical points we have maintained the same longitude (0\({}^{\circ}\)), since these will allow us to show the great variations of the RD as a function of altitude and latitude.  
In this work, we have focused on the RD that atmospheric neutrons deposit in human tissues, if the readers want to know the effects of charged particles, they can read for example [6; 8; 10].