With this numerical model, we can simulate the propagation of Alfvén waves from Io at various points along Io’s orbit. First, consider a case where Io is near the centrifugal equator, so that the Alfvén travel times from Io to each hemisphere are approximately the same. The Pedersen conductance of both ionospheres is set at 1 mho for these runs. Figure 2 shows the parallel component of the wave Poynting flux for such a case, 40 minutes from the start of the run. Io starts at 85° longitude (at the right side of the figure) and propagates westward. Note that Io crosses the centrifugal and magnetic equators at 74.3°. In this figure, red colors indicate northward Poynting flux while blue colors indicate southward flux, with the intensity of the colors indicating the magnitude. The magnitude of the Poynting flux is scaled by the background magnetic field to account for the smaller flux tube radius as the wave approaches each ionosphere. Figure 2a shows the results from the low-density case, while the high-density case is given in Figure 2b. As expected, the northern and southern wave patterns are approximately symmetric. At these longitudes, the dense torus extends about 10°-15° of latitude on either side of the equator. An animation of the run shown in Figure 2a is given in Supporting Information S1.