Monte Carlo simulation of CRAND protons trapped at low Earth orbits

• Published in: Advances in space research 2022-01, Vol.69 (1), p.197-208
• Main Authors: Sarkar, Ritabrata, Roy, Abhijit
• Format: Article
• Language: English
• Subjects: CRAND protons; Monte Carlo simulation; Radiation belt; Trapped protons at low Earth orbit
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/j.asr.2021.10.006

•Production and entrapment of the CRAND protons at the low Earth orbit.•Event by event simulation procedure using Monte Carlo technique.•Comparison of trapped protons measured by PAMELA and simulated results.•Trapped proton distribuiton in the radiation belt and discussions on the features. The Cosmic Ray Albedo Neutron Decay (CRAND) is believed to be the principal mechanism for the formation of inner proton radiation belt – at least for relatively higher energy particles. We implement this mechanism in a Monte Carlo simulation procedure to calculate the trapped proton radiation at the low Earth orbits, through event-by-event interaction of the cosmic ray particles in the Earth’s atmosphere and their transportation in the magnetosphere. We consider the generation of protons from subsequent decay of the secondary neutrons from the cosmic ray interaction in the atmosphere and their transport (and/or trapping) in the geomagnetic field. We address the computational challenges for this type of calculations and develop an optimized algorithm to minimize the computation time. We consider a full 3D description of the Earth’s atmospheric and magnetic-field configurations using the latest available models. We present the spatial and phase-space distribution of the trapped protons considering the adiabatic invariants and other parameters at the low Earth orbits. We compare the simulation results with the trapped proton flux measurements made by PAMELA experiment at low Earth orbit and explain certain features observed by the measurement.