“…There are a variety of acceleration and loss mechanisms that affect electron flux variations and corresponding pitch angle distributions (PADs), such as wave‐particle interactions (Hua et al, 2019; Huang et al, 2015; Ni et al, 2019; Summers et al, 2007, 2009; Tang et al, 2014; H. Zhao, Ni, et al, 2019) and magnetospheric compression by enhanced solar wind activities (Ni, Xiang, et al, 2016; Shprits et al, 2006; Yuan & Zong, 2013). In such a case, the long‐term statistical characteristics of different electron PADs are very important dynamic properties of energetic electrons, which provide essential indicators to understand the physical processes of electron transport, energization, and loss (Liu et al, 2020; Ni, Zou, et al, 2016; Peng et al, 2020; Shi et al, 2016; Tang & Summers, 2019; H. Zhao et al, 2018; Zhong et al, 2020).…”