Authors: William Ryan (West Virginia University), Paul Cassak (West Virginia University), Haoming Liang (University of Maryland, College Park; NASA GSFC), Ida Svenningsson (Uppsala University, Sweden; Swedish Institute of Space Physics, Uppsala, Sweden) Giulia Cozzani (University of Helsinki, Finland)

In many space plasmas, including the solar wind and magnetosheath, electron instabilities drive the generation of whistler waves (e.g., Kretzschmar et al., A&A 656, A24, 2021, Huang et al., ApJ, 861:29, 2018). One commonly studied instability is the whistler anisotropy instability. The conditions for the whistler anisotropy instability to occur have been well studied (e.g., Gary and Wang, JGR, 101, 10749, 1996). In this study, we reinvestigate the whistler anisotropy instability using an approach to non-LTE dynamics based on kinetic entropy (Cassak et al., PRL, 130, 085201, 2023). We use this entropic approach to understand the system after the whistler anisotropy instability saturates. We perform 2.5D particle-in-cell simulations of the whistler anisotropy instability and show that it agrees with predicted properties of the saturated wave. This work may be useful for comparison to well-resolved data of the whistler anisotropy instability taken from Magnetospheric Multiscale (MMS) satellites (e.g., Ahmadi et al., JGR, 123, 8, 2018; Kitamura et al., JGR, 125, 5, 2020; Svenningsson et al., JGR, 129, e2024JA032661, 2024).