Abstract. Pc5 ULF (ultra-low frequency) waves can energize electrons to relativistic energies of >2 MeV in geostationary orbits. Enhanced fluxes of such electrons can induce operational anomalies in geostationary satellites. The variations of the two quantities in timescales ranging from days to solar cycles are thus of interest in gauging their space weather effects over different time frames. In this study, we present a statistical analysis of two 11-year solar cycles (cycles 22 and 23) of data comprising the daily relativistic electron fluence observed by Geostationary Environment Satellites (GOESs) and daily Pc5 ULF wave power derived from auroral zone magnetic observatories in Canada. First, an autocorrelation analysis is carried out, which indicates a 27 d periodicity in both parameters for all solar phases, and such a periodicity is most pronounced in the declining and late declining phase. Also, a 9 and 13 d periodicity are seen in some years. Then, a superposed epoch analysis is performed to scrutinize semiannual variation (SAV), which shows that fluence near the equinoxes is 1 order of magnitude higher than near solstices, and Pc5 ULF wave power is 0.5 orders of magnitude higher near the equinoxes than near the solstices. We then evaluate three possible SAV mechanisms (which are based on the axial, equinoctial, and Russell and McPherron effect) to determine which one can best explain the observations. Correlation of the profiles of the observational curves with those of the angles that control each of the SAV mechanisms suggests that the equinoctial mechanism may be responsible for the SAV of electron fluence, while both the equinoctial and the Russell and McPherron mechanisms are important for the SAV of Pc5 ULF wave power. Comparable results are obtained when using functional dependencies of the main angles instead of the angles mentioned above. Lastly, superposed curves of fluence and Pc5 ULF wave power were used to calculate least-square fits with a fixed semiannual period. Comparison of the maxima and minima of the fits with those predicted by the three mechanisms shows that the equinoctial effect better estimates the maxima and minima of the SAV in fluence while for the SAV in Pc5 ULF wave power the equinoctial and Russell and McPherron mechanisms predict one maximum and one minimum each.

中文翻译：

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Pc5 超低频 (ULF) 波和相对论电子在两个太阳周期观测中的半年变化：与经典假设的预测比较

摘要。Pc5 ULF（超低频）波可以在地球静止轨道中将电子激励到大于 2 MeV 的相对论能量。这种电子的增强通量会导致对地静止卫星的运行异常。因此，这两个量在从天到太阳周期的时间尺度上的变化对于衡量它们在不同时间范围内的空间天气影响很感兴趣。在这项研究中，我们对两个 11 年太阳周期（周期 22 和 23）的数据进行了统计分析，这些数据包括地球静止环境卫星 (GOES) 观测到的每日相对论电子注量和来自极光区磁观测站的每日 Pc5 ULF 波功率在加拿大。首先，进行自相关分析，这表明所有太阳相位的两个参数都有 27 d 的周期性，这种周期性在下降和下降后期最为明显。此外，在某些年份可以看到 9 天和 13 天的周期性。然后，进行叠加历元分析以仔细检查半年变化（SAV），结果表明，春分点附近的注量比近至点高 1 个数量级，Pc5 ULF 波功率在春分点附近比近点高 0.5 个数量级。至点。然后，我们评估了三种可能的 SAV 机制（基于轴向、春分以及罗素和麦克弗伦效应）以确定哪一种机制最能解释观察结果。观测曲线的轮廓与控制每个 SAV 机制的角度的轮廓的相关性表明，春分机制可能是电子注量 SAV 的原因，而春分和罗素和麦克弗伦机制对于 Pc5 ULF 波功率的 SAV 都很重要。当使用主角度的函数依赖而不是上面提到的角度时，可以获得可比较的结果。最后，注量和 Pc5 ULF 波功率的叠加曲线用于计算具有固定半年周期的最小二乘拟合。拟合的最大值和最小值与三种机制预测的比较表明，春分效应更好地估计了 SAV 影响的最大值和最小值，而对于 Pc5 ULF 波功率中的 SAV，春分和 Russell 和 McPherron 机制预测了一个最大值和最小值各一个。当使用主角度的函数依赖而不是上面提到的角度时，可以获得可比较的结果。最后，注量和 Pc5 ULF 波功率的叠加曲线用于计算具有固定半年周期的最小二乘拟合。拟合的最大值和最小值与三种机制预测的比较表明，春分效应更好地估计了 SAV 影响的最大值和最小值，而对于 Pc5 ULF 波功率中的 SAV，春分和 Russell 和 McPherron 机制预测了一个最大值和最小值各一个。当使用主角度的函数依赖而不是上面提到的角度时，可以获得可比较的结果。最后，注量和 Pc5 ULF 波功率的叠加曲线用于计算具有固定半年周期的最小二乘拟合。拟合的最大值和最小值与三种机制预测的比较表明，春分效应更好地估计了 SAV 影响的最大值和最小值，而对于 Pc5 ULF 波功率中的 SAV，春分和 Russell 和 McPherron 机制预测了一个最大值和最小值各一个。