Abstract. Long-term variations of the relativistic (~ MeV) electrons in the Earth's radiation belt are explored to study seasonal features of the electrons. An L-shell dependence of the seasonal variations of the electrons is revealed for the first time. A clear ~ 6-month periodicity is identified for 1.5–6.0 MeV electron fluxes in the L-shells between ~ 3.0 and ~ 5.0, representing two peaks per year. The two-peak variation is strong during solar cycle descending to minimum phases, with weaker/no variations during solar maximum. The peaks are largely asymmetric in amplitude. These are not essentially equinoctial: sometimes the peaks are shifted to solstices and sometimes one annual peak is only observed. No such seasonal features are prominent for L 5.0. The results imply varying solar/interplanetary drivers of the radiation belt electrons at different L-shells. This has a potential impact on the modeling of space environment. Plausible solar drivers are discussed.

中文翻译：

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地球辐射带的季节性依赖性：新见解

摘要。探索了地球辐射带中相对论（〜MeV）电子的长期变化，以研究电子的季节性特征。首次揭示了电子季节性变化的L壳依赖性。在L壳层中约1.5至6.0 MeV的电子通量，在〜3.0至〜5.0之间，具有清晰的〜6个月周期，代表每年两次高峰。在太阳周期下降到最小相位期间，两峰变化很大，而在太阳最大值时，变化较弱/没有变化。峰的幅度在很大程度上是不对称的。这些本质上不是等分的：有时峰移至孤峰，有时仅观察到一个年度峰。L 5.0没有这样的季节性特征。结果表明，在不同的L壳层，辐射带电子的太阳/行星际驱动器发生了变化。这对空间环境的建模有潜在的影响。讨论了合理的太阳能驱动器。