a standing wave would be when the waves reinforce each other as opposed to cancelling each other out. if it were a standing wave and not phase-cancelled then the amplitude would be greatest in the y and z axis…
so to create a scalar wave, the EM waves need to be 180 degrees out of phase (halfway through the full waveform, with the peak of one being in line with the trough of the other) ??
this should leave a 'jagged', most likely higher frequency (due to the macro non-conformities to the perfect wave value present in both the waves) - i'm unfamiliar with the mechanics of scalar waves but this seems to be a diminuation of amplitude, albeit with the excess energy going somewhere, i'm just struggling to see how it wouldn't randomly dissipate, with the excess energy losing coherence and therefore relevance in relation to the remaining wave…