NSWP: Theoretical Modeling of the Inner Radiation Belt, II

该项目将构建一个关于地球内辐射带质子和轻离子的综合理论模型。该模型将基于现有的简化质子模型。它将描述内部区域的完全空间相关性、能量相关性和太阳周期时间相关性。模型的组成部分将包括：对反照率中子衰减源的蒙特卡罗模拟；注入太阳质子和氦；捕获质子与中性大气核反应产生的二次轻离子源；中性大气电离的能量损失，以及电离层和等离子体层中自由电子的能量损失，与太阳活动历史记录的太阳周期有关；基于来自地磁记录和国际地磁参考场的多极地球磁场模型的绝热压缩粒子加速；计算中子衰减源和大气密度漂移平均值和刚性捕获极限的捕获粒子轨迹数值跟踪；来自中性大气的被捕获粒子的核散射，包括弹性和非弹性过程；具有经验确定的扩散系数的径向扩散；以及被捕获的放射性次级粒子的衰变。所得到的模型将与现有的辐射带数据和经验模型进行比较以进行验证。该模型将为理解辐射带内区发生的物理过程提供一个框架。拟议的对每个模型组件的相对重要性的定量研究将导致对主导物理机制的新理解。特别是，将确定被捕获粒子的寿命和重大损失机制，将评估外部源(径向扩散)和内部源(中子衰变和核反应)的相对重要性，并将确定对填充内辐射带具有重要意义的核反应。一个精确的内辐射带模型将对确定近地轨道的危险辐射环境具有实用价值。目前的经验模型在航天器设计中被广泛使用，但缺乏将在本工作中讨论的详细的能量、空间和时间变化。

This project will construct a comprehensive theoretical model of the Earth's inner radiation belt protons and light ions. The model will be based on an existing simplified proton model. It will describe the inner zone's full spatial dependence, energy dependence, and solar cycle time dependence. Components of the model will include: Monte Carlo simulation of the albedo neutron decay source; injection of solar protons and helium; secondary sources of light ions from nuclear reactions of trapped protons with the neutral atmosphere; energy loss to ionization of the neutral atmosphere, and to free electrons in the ionosphere and plasmasphere, with solar cycle dependence from the historical solar activity record; particle acceleration by adiabatic compression based on multipole geomagnetic field models from the archeomagnetic record and the International Geomagnetic Reference Field; numerical trapped particle trajectory tracing to calculate drift averages of the neutron decay source and the atmospheric densities, and the rigidity trapping limits; nuclear scattering of the trapped particles from the neutral atmosphere, including elastic and inelastic processes; radial diffusion with empirically determined diffusion coefficients; and decay of radioactive trapped secondaries. The resulting model will be compared to existing radiation belt data and empirical models for validation. The model will provide a framework for understanding the physical processes occurring in the inner zone of the radiation belt. The proposed quantitative study of the relative importance of each model component will lead to a new understanding of the dominant physical mechanisms. In particular, the lifetimes and significant loss mechanisms of the trapped particles will be determined, the relative significance of the external (radial diffusion) and internal (neutron decay and nuclear reaction) sources will be evaluated, and the nuclear reactions that are significant for populating the inner radiation belt will be identified. An accurate model the inner radiation belt will be of practical value for specifying the hazardous radiation environment in low Earth orbit. Current empirical models are used extensively in spacecraft design but are lacking in the detailed energy, spatial, and temporal variations that will be addressed in this work.