This discussion will probably warp to the starship & technology forum, but anyway:The depiction of the warp field in the TNGTM suggests it is static, but actually it has a certain frequency due to the ignition sequence of the coils. The subspace distortion in cochranes eventually determines the warp speed (note that v/c is always equal to the cochrane value).
1. The subspace distortion gets stronger as the power output is increased.
2. The subspace distortion gets stronger, as a cretain threshold is exceeded, given by the nature of subspace and the principle of warp drive to create nested layers of the field. To generate more layers at a time, it is obvious that the frequency has to be increased.
Don't ask me about the nature of these layers, they don't exactly fit into the theory of just creating a field or wave, maybe it is an effect of field overlay (i.e. modulation).
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"Invaders from the fifth dimension!" - or: the canon proof that subspace is the same as hyperspace
Ex Astris Scientia