Evolution of the solar wind as the Alfvén waves propagate through the corona. The fluctuating velocity and magnetic field components are shown in panels a and b. The density perturbations defined as δρ/ρ, where δρ = ρ − ⟨ρ⟩ and ⟨ρ⟩ is the density averaged over 10 min intervals, are shown in panel c. Panel d is a simulation snapshot of v_ϕ at τ = 1000 min. The dashed arrows in panels a and b highlight the apparent bifurcation of v_ϕ and B_ϕ.