In this work an improved approach of existing approximations on the coupling function between primary and ground-level cosmic-ray particles is presented. The proposed coupling function is analytically derived based on a formalism used in Quantum Field Theory calculations. It is upgraded compared to previous versions with the inclusion of a wider energy spectrum that is extended to lower energies, as well as an altitude correction factor, also derived analytically. The improved approximations are applied to two cases of Forbush decreases detected in March 2012 and September 2017. In the analytical procedure for the derivation of the primary cosmic-ray spectrum during these events, we also consider the energy spectrum exponent \(\gamma \) to be varied with time. For the validation of the findings, we present a direct comparison between the primary spectrum and the amplitude values derived by the proposed method and the obtained time series of the cosmic-ray intensity at the rigidity of 10 GV obtained from the Global Survey Method. The two sets of results are found to be in very good agreement for both events as denoted by the Pearson correlation factors and slope values of their scatter plots. In such way we determine the validity and applicability of our method to Forbush decreases as well as to other cosmic-ray phenomena, thus introducing a new, alternative way of inferring the primary cosmic-ray intensity.

在这项工作中，提出了对初级和地面宇宙射线粒子之间耦合函数的现有近似的改进方法。提出的耦合函数是基于量子场论计算中使用的形式主义分析导出的。与以前的版本相比，它进行了升级，包括更宽的能谱，可扩展到更低的能量，以及高度校正因子，也是通过分析得出的。改进的近似值应用于 2012 年 3 月和 2017 年 9 月检测到的 Forbush 减少的两个案例。 在这些事件期间推导初级宇宙射线谱的分析程序中，我们还考虑了能谱指数\(\gamma \)随时间而变化。为了验证研究结果，我们直接比较了由所提出的方法得出的初级光谱和振幅值与从全球调查方法获得的 10 GV 刚度下宇宙射线强度的时间序列之间的直接比较。发现两组结果对于这两个事件非常一致，如 Pearson 相关因子和散点图的斜率值所示。通过这种方式，我们确定了我们的方法对 Forbush 衰减以及其他宇宙射线现象的有效性和适用性，从而引入了一种新的替代方法来推断初级宇宙射线强度。