Authors: Tien Vo (LASP - CU Boulder), Oleksiy Agapitov (SSL - UC Berkeley), Robert Ergun (LASP), Cynthia Cattell (U of Minnesota), Jack Redepenning (U of Minnesota)

The role of whistlers in scattering strahl electrons in the solar wind has been a subject of active research in recent years due to new observations by the Parker Solar Probe (PSP). There were strong whistler activities throughout PSP’s Encounter 1. Especially, high-amplitude whistlers are often found at the boundaries of switchbacks, where the magnetic inhomogeneity is high, although whistlers are also observed at magnetic dips unrelated to switchbacks. Recent studies also suggest that the occurrence of whistlers close to the Sun is associated with magnetic activity. As such, the local magnetic field is an important factor on the propagation of whistler waves, which could result in reflection, refraction, absorption, or mode conversion. In this study, we utilize test particle simulations to parameterize the efficiency of wave-particle interactions in terms of the magnetic inhomogeneity and wave amplitude. We show that the background magnetic field can enable effective scattering of the strahl even for parallel whistlers.