Eckard
Many thanks re; 'forerunner'. First, Steve is one of the few who understands almost completely. 2nd; I would say your 'knowledge' is not 'wrong', but understanding too incomplete to date to fully rationalise. I explain below, but 3rd; The 'forerunner' is simply the 2nd part of the 'birefringence' found by Raman. There was scant space for this, so to clarify; In some media (i.e. birefringent and diffuse matter) The emissions only interact progressively, so the part which has not yet coupled indeed carries on undelayed on the old axis (we call 'vector'). Subject to particle characteristics, i.e multiple spin types, we will find 3 (tri-refringence) or more axis at once. In space this process may take many kiloparsecs. The observed effects in that case are gradual 'curvature' of the light and weak 'gravitational' lensing, which is density dependent.
But now back to your; "speed of propagation refers to the medium but neither to the emitter nor to the receiver." Which is both entirely true and fully consistent with the above, but this will initially test your intellect!;
The immediate instantaneous emission is wrt the EMITTER. This is indeed however only as far as the transition zone (TZ) between the near and far field, (which I thank you for flagging up) because the 'medium' WITHIN the TZ (the near field) is in the same kinetic state as the emitter. The TZ is therefore the frame boundary. Thereafter the emitted 'signal' changes speed to c wrt the FAR FIELD, which is the medium OUTSIDE the TZ, which we call the 'Local Background' of the emittter, or the 'next frame up'.
The distance to the TZ may be less than a micron, or 100+km (Earth's bow shock), or 100+ au's ('AU' is now 'au' by the way) to the sun's heliosheath, or, for the galaxy, the Halo. Remember there may be infinitely many smaller spaces ('s') within each and every larger space ('S'), precisely as specified by Einstein (1952).
So Pentcho's emission theory is correct in a very local domain, but then also correct in lots more local domains (frames) at all scales, which may be DIFFERENT to the first. Re-emission is always at c. (I was delighted to find Dowdye's earlier consistent thesis, but rather after developing the DFM - so he's guilty of common anticipatory plageurism!)
The process is symmetrical, so a reflector is also an emitter. Light arrives at the fine structure TZ of the mirror, is changed to c wrt the mirror, is absorbed again and re-emitted at c wrt the mirror, but on re-negotiating the TZ does exactly what all other emissions do, changes to c wrt the medium. That explains one of the biggest inconsistencies in current theory (along with many others).
If that doesn't seem entirely logical after a couple of re-reads please do say why and I'll try to explain it better.
I've suggested a few verification experiments in the imminent Hadronic Jouranl Paper discussing Kantor and mirrors.
Best wishes
Peter