In the case of Io (θ = 90), scenario #1 is the way the hybrid code would be set up. However to look at parallely propagating waves don't we need to have to have k along B, as is shown in scenario #2? But is a setup like #2 problematic because the plasma is passing perpendicular to the 1-dimension axis? I can see why Bob's dispersion code would not work for #1 but it would work for #2, right?

This is what I was thinking about for my exam proposals, not for AGU. The exam proposals are just for the exam, and do not necessarily have to be carried out.

But for AGU, is scenario #3 appropriate for oblique propagation? I believe my confusion is coming from whether or not we have to consider the x-axis to always be the direction of plasma flow (i.e. we always consider the plasma to be flowing in the torus direction). The hybrid code currently allows the direction of B to change with respect to the x-axis, but not the direction of plasma flow. So in this case, how is it possible to set up the code for scenario #2 or #3? Is it a matter of changing the function that loads the particles in phase space?