Simulation of Cosmic Rays Trajectories and Neutron Transport generated on the Sun and observed on Earth

The study of Cosmic Rays (CRs) and Solar Energetic Particles (SEPs) is key in analyzing the effect of solar activity on the terrestrial environment. Changes in the properties of the medium they pass through until their detection profoundly affect the intensity and the propagation direction of the CR flux.

Our starting point is that accurate measurements of CR and SEP flux can allow us to infer the conditions of the medium they pass through on their way to Earth, particularly the interplanetary medium, the magnetosphere and the atmosphere. The development of a CR simulation code helps us perform such analysis, which may contribute to future predictions of solar events and prevent potential damage and disturbances in the global technological system and the human environment. Computational simulation of these phenomena allows us to interpret the data and obtain a vision that will facilitate, for instance, explaining the generation and transport of solar neutrons to Earth’s atmosphere and their interaction with the atmosphere and the detectors installed in different geographical locations.

The Space Research Group of the University of Alcala (SGR – UAH) has extensive experience in the design, construction, control and maintenance of neutron measurement systems, distributed in different regions of the world. Among these, we can mention: CALMA, ORCA, ICaRO and the EPD aboard on the Solar Orbiter Mission. These instruments generate a large amount of data that must be analyzed and modeled for understanding and study. It is at this point where computational simulation techniques and data management are crucial for the SGR-UAH group.

In this work we present the code we developed to study the trajectory and rigidity of charged particles entering Earth’s magnetic field. The simulation code TOROS (Trajectories of cOsmic Rays Observed Simulator) is based on numerically calculating the trajectories of charged particles and their interaction with Earth’s magnetic field before reaching the atmosphere. The code uses the magnetic dipole model and various approximations of Tsyganenko’s magnetic field model. Our goal is to use this simulation tool and the data it generates as input for well known simulation codes in the research field, such as GEANT-4 and CORSIKA, to validate, simulate and propose models based on experimental measurements from detectors of the SGR-UAH group and others worldwide. Comparing our results with other simulation codes is also part of the validation and testing process for the “TOROS” code.