NSWP: Theoretical Modeling of the Inner Radiation Belt, II

本项目将构建地球内辐射带质子和光离子的综合理论模型。该模型将基于现有的简化质子模型。它将描述内区完全的空间依赖性、能量依赖性和太阳周期时间依赖性。该模型的组成部分将包括：反照率中子衰变源的蒙特卡罗模拟；太阳质子和氦的注入；被困质子与中性大气核反应产生的光离子的二次来源；中性大气电离的能量损失，以及电离层和等离子层中的自由电子的能量损失，与太阳活动历史记录的太阳周期相关；基于古地磁记录和国际地磁参考场多极磁场模型的粒子绝热压缩加速；用数值追踪捕获粒子轨迹计算中子衰变源漂移平均值和大气密度，以及刚性捕获极限；中性大气中捕获粒子的核散射，包括弹性和非弹性过程；具有经验确定扩散系数的径向扩散；以及放射性二次阱的衰变。所得模型将与现有辐射带数据和经验模型进行比较验证。该模型将为理解发生在辐射带内区的物理过程提供一个框架。提出的对每个模型组成部分的相对重要性的定量研究将导致对主要物理机制的新理解。特别是，将确定捕获粒子的寿命和重要损失机制，评估外部（径向扩散）和内部（中子衰变和核反应）源的相对重要性，并确定对填充内辐射带具有重要意义的核反应。精确的内辐射带模型对确定近地轨道辐射危险环境具有实用价值。目前的经验模型在航天器设计中广泛使用，但缺乏详细的能量、空间和时间变化，这些将在本工作中得到解决。

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.