Modeling the Dynamics of Energetic Protons in Earth's Inner Magnetosphere
Modeling the Dynamics of Energetic Protons in Earth's Inner Magnetosphere
复制标题
DOI：
10.1029/2021ja030153
复制
发表时间：
2022-03
期刊：
影响因子：
--
通讯作者：
X. Lyu;W. Tu
中科院分区：
文献类型：
--
作者：
X. Lyu;W. Tu
最近，货车艾伦探测器的数据揭示了地球内磁层中高能质子的有趣的能量依赖动力学。为了量化径向扩散和电荷交换对所观察到的环电流质子的能量依赖动力学的作用，实现了具有电荷交换损失的一维径向扩散模型。首先将2012年11月至2013年9月长期观测到的质子通量转换为相空间密度，然后通过我们的模型进行模拟，该模型由来自数据的L* = 5.5的外边界条件驱动。模拟结果表明，我们的模型一般捕获的能量质子的传输和加速在μ = 30，50和80 MeV/G和K = 0.11 G1/2 RE，表明径向扩散的主要来源机制>75 keV的质子在L* = 3.5-5.5。此外，在较低μ下观察到的质子快速衰变和在较高μ下观察到的质子缓慢衰变被模型很好地捕获，证明了电荷交换在解释观察到的能量依赖性质子衰变中的主导作用。对于更高的μ质子，在很宽的L* 范围内观察到以小时为时间尺度的质子迅速损失，这太快而不能用电荷交换来解释。在高L* 区域的一些即时损失再现的模型与向外的径向扩散到外边界。然而，在较低的L* 区域观察到的许多即时损耗没有被模型捕获，这可能是由于其他损耗机制，包括电磁离子回旋波散射和场线曲率散射。
Recently, Van Allen Probes data have revealed the interesting energy‐dependent dynamics of energetic protons in Earth's inner magnetosphere. To quantify the role of radial diffusion and charge exchange to the observed energy‐dependent dynamics of ring current protons, a 1D radial diffusion model with charge exchange loss is implemented. The observed proton flux over the long‐term period of November 2012 to September 2013 is first converted to phase space densities, which are then simulated by our model driven by an outer boundary condition at L* = 5.5 derived from the data. The simulation results show that our model generally captures the transport and acceleration of energetic protons at μ = 30, 50, and 80 MeV/G and K = 0.11 G1/2 RE, suggesting that radial diffusion is the dominant source mechanism for >75 keV protons at L* = 3.5–5.5. In addition, the observed fast decay of protons at lower μ and slow decay at higher μ are well captured by the model, demonstrating the dominant role of charge exchange in explaining the observed energy‐dependent proton decay. For higher μ protons, prompt losses of protons on the time scale of hours are observed over a wide range of L*, which is too fast to be explained by charge exchange. Some of the prompt losses at high L* regions are reproduced by the model with outward radial diffusion to the outer boundary. However, many prompt losses observed at lower L* regions are not captured by the model, which could be due to other loss mechanisms including electromagnetic ion cyclotron wave scattering and field line curvature scattering.