Contours of proton VD for run 4 at τ = 0 (dashed gray) and at τ = 31 (solid red), when the forward-half of VD is shaped by the kinetic shells (blue) that were found relevant for the hammerhead populations reported by PSP (Verniero et al. 2022). The diffusion contours v_⊥(v_∥) were computed by linking the proton coordinates (v_∥, v_⊥) (green squares) with the resonant wave frame (v_ϕ, r/v_A = 1.3, 0.0) (black dot) and ${\stackrel{\sim }{k}}_r=0.60$. The slope of these lines, such as the green line, is v_⊥/[v_∥ − v_ϕ], with v_∥ and v_⊥ calculated using Eqs. (14) and (15) in Isenberg & Lee (1996).