During geomagnetic storms, the ring current ions sometimes exhibit rapid loss as suggested by the fast recovery of the Dst index on a time scale of a few hours. The effects of magnetic field line curvature (FLC) scattering on the loss of ring current ions, which have not been well quantified, are studied here by test particle simulations under the T89c magnetic field model. Our simulation results show that the prediction of ion loss based on a single‐value cutoff of the κ parameter or maximum of of a single FLC scattering is not accurate. Instead, the e‐folding lifetime (τ) for the loss of ring current ions due to cumulative FLC scattering has been calculated for different initial ion energies, equatorial pitch angles, and L shells under different geomagnetic conditions. The results show that in general the FLC scattering loss is faster for ions of higher energy, higher mass, smaller pitch angle, higher L, and at high Kp level. Specifically, we find that at Kp = 6 the lifetime can be <10 h at L > 5 for 100 s keV protons and at L > 4 for 100 s keV O⁺, which demonstrates that FLC scattering can be an important mechanism for the observed fast loss (τ < 10 h) of ring current ions during geomagnetic storms. Furthermore, we formulate an empirical formula for τ as a function of ion energy, pitch angle, position, species, and Kp. The empirical formula can be directly included in ring current models to account for the FLC scattering effects.

中文翻译：

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量化磁力线曲率散射对环电流离子损失的影响

在地磁风暴期间，环流离子有时会表现出快速损耗，这是Dst指数在几小时的时间范围内快速恢复所暗示的。在T89c磁场模型下，通过测试粒子模拟，研究了尚未很好量化的磁场线曲率（FLC）散射对环电流离子损失的影响。我们的模拟结果表明，基于κ参数的单值截止或单个FLC散射最大值的离子损失预测是不准确的。相反，电子折叠寿命（τ），对于不同的初始离子能量，赤道俯仰角和在不同地磁条件下的L壳层，已经计算出了由于累积FLC散射而导致的环电流离子的损失。结果表明，一般而言，对于能量较高，质量较高，螺距角较小，L较高和Kp较高的离子，FLC散射损耗更快。具体而言，我们发现在Kp  = 6时， 对于100 s keV质子，L > 5时的寿命可以为<10 h； 对于100 s keV O ^+而言，L > 4时，寿命可以<10 h ，这表明FLC散射可能是观察到的重要机制。快速损失（τ 在地磁暴期间，环电流离子<10 h）。此外，我们针对离子能量，桨距角，位置，种类和Kp公式化了τ的经验公式。经验公式可以直接包含在环电流模型中，以说明FLC散射效应。