Monte Carlo Simulation of CRAND Protons Trapped at Low Earth Orbits

TL;DR

This paper presents a Monte Carlo simulation of CRAND protons trapped at low Earth orbits, modeling their generation, transport, and trapping in Earth's magnetic field, and compares results with PAMELA measurements.

Contribution

It introduces an optimized Monte Carlo simulation incorporating full 3D Earth models to study CRAND protons at low Earth orbits, addressing computational challenges.

Findings

Simulation results match PAMELA measurements

Distribution of trapped protons explained by adiabatic invariants

Enhanced understanding of CRAND mechanism at low Earth orbits

Abstract

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.