Sensitivity of Bounce‐Averaged Diffusion Coefficients to the Latitudinal Variability of Lightning Generated Whistlers

The development of statistical wave models that include the underlying variability of the wave distributions is an important next step toward more accurate radiation belt models. Lightning‐generated whistlers (LGW) are an important wave mode in the plasmasphere; previous time‐averaged diffusion coefficients have used assumptions about the wave distributions as a function of magnetic latitude. Shane et al. (2025, https://doi.org/10.1029/2025ja034164 ) compiled a comprehensive data set of observed event‐based LGW wave distributions using Van Allen Probes measurements. In this study, ray tracing is used to model the wave propagation to provide improved assumptions about the LGW wave variability along a magnetic field line for a source lightning discharge. The peak wave frequency increases with increasing magnetic latitude, symmetrically about the magnetic equator. The wave normal angle distribution has two components: (a) a latitudinally varying component that arises from the initial propagation of waves and (b) a component that is constant with latitude, arising from the magnetospherically reflecting waves. Bounce‐averaged diffusion coefficients are calculated using analytical wave distributions with different assumptions for the latitudinal variation of waves to quantify the sensitivity. Since the wave distributions at the equator are similar between different assumptions, the diffusion coefficients are not overly sensitive to the choice of frequency spectrum variation. However, enhanced pitch angle scattering at MeV energies occurs with the choice of the latitudinally varying wave normal angle distribution. These improved assumptions about the latitudinal wave distributions will be used in future work to calculate event‐based bounce‐averaged diffusion coefficients from the database of single point Van Allen Probes LGW observations.