“…As is a very common approach in such numerical experiments (e.g., see Allanson et al., 2019, 2020; Camporeale, 2015; Camporeale & Zimbardo, 2015; H. Chen et al., 2017, 2018; Gao et al., 2017; Kuzichev et al., 2019; Liu et al., 2010, 2012; Tao et al., 2011, 2017), we consider one field‐aligned dimension (x), which is a reasonable approximation near the magnetic equator (i.e., uniform fields and field‐aligned wave propagation) (Tsurutani & Smith, 1977), i.e., the region that is most important for whistler‐mode wave generation (Gao et al., 2014; W. Li et al., 2010, 2012; Teng et al., 2018). We therefore use the one‐dimensional version of the EPOCH code, such that all quantities have spatial gradients in the x ‐direction only.…”