Electromagnetic waves with E parallel to B

Two explanations of how to obtain electromagnetic waves with E parallel to B are presented. It is noted that, contrary to what is implicitly assumed, electromagnetic waves with the electric field parallel to the magnetic field are not general solutions to Maxwell´s equations in the same sense that the conventional E-perpendicular-to-B solutions are. Both solutions are shown to follow from boundary conditions. The first solution results from a misapplication of the principle of superposition. One cannot fix the values of the arbitrary constants used in the principle of superposition and retain the features of a general solution. When restrictive conditions are applied to the problem, the solution is no longer a general solution, but instead a solution to a boundary value problem. The second solution is even more restrictive than the first because it fixes functions along two different parametric lines of space-time. These standing-wave solutions to Maxwell´s equations are not surprising, however, when boundary conditions are imposed, and with this understanding the E-parallel-to-B solutions are not unexpected