Roy Lewallen wrote:
But in a tightly wound inductor, a field created by the current in one
turn is coupled almost instantly to all the other turns ...

"All the other turns"? Here's what Jim Lux, W6RMK, had to say
about that:

"For inductance the signficant thing is that the magnetic field
of one segment pretty much links to the adjacent segments, and
less so for the rest."

Less to the 3rd, less than that to the 4th, even less than that
to the 5th. What do you think it might be by the time it gets
to the 80th turn on Tom's coil? Seems that we can assume that
the linkage between coil #1 and coil #80 is negligible.

Once again it's necessary to point out that I'm speaking here of an
inductor which has very good coupling between turns and minimal field
leakage or radiation, ...

So was W6RMK.

There's no magic transition point.

Indeed there isn't. I repeat, in case your didn't understand -
indeed there isn't. So you can discard your magic lumped-
circuit model for a system containing reflections.
--
73, Cecil http://www.qsl.net/w5dxp