If I understand what you are saying then a vertical EM ground wave
suffers from non-linear [distortion], as you define it.

The surface component of the wave is in a dielectric media, earth
ground, with a propagation constant less than the velocity of light.
While the top of the EM wave is propagating in a 377 ohm medium, air,
with a velocity of propagation close to the velocity of light. So, the
top of the wave travels faster than the bottom and the wave tilts in the
direction of propagation and ultimately 'falls' to earth.

You are implying that a wave from a single source but traveling in two
or more different mediums suffer non-linearity. Doesn't that mean that
non-linearity is applicable to all EM waves involved in different media?

I believe that Maxwell-Heaviside's Curl equations at the boundary
conditions can be solved for this condition. [It's been over 40 years
since I tried it though!]

I have a problem with the words 'non linear as used in this thread.
'Non-linearity' is generally understood to introduce harmonics, i.e.
distortion.

For an EM wave sharing a common boundary in different linear media I
offer that the wave 'rolls' in the direction of propagation but does not
create harmonics from some non-linear process.

Deacon Dave, W1MCE
+ + +

[SNIP]

Nonlinearity is if the velocity varies with the amplitude of the wave. Like
in acoustics where the positive (high-pressure) peaks propagate faster than
the negative peaks. It leads to waveform distortion and creation of
harmonics. The modern cardiology ultrasound scanners ( 5 years old) usually
default to this mode these days, transmitting ultrasound at about 3 MHz,
receiving at 6 MHz, as it gives better image quality than the fundamental
mode.


Sverre
www.qsl.net/la3za