Reg, G4FGQ wrote:
"What`s that stuff which clearly flows between the plates of a
wide-spaced capacitor?"

It is displacement current as Reg and Cecil know very well. J.C.
Maxewell speculated long ago that displacement current is surrounded by
magnetic flux, same as conducting current is. That was the key to
electromagnetic radiation which explains how the radiated fields
replenish each other where there is no matter.

As there is displacement current between the tips of a horizontal dipole
and the earth, and the voltage vector is vertical in this voltage
stress, radiation from this source is vertically polarized. The main
(high intensity) radiation from a horizontal dipole is horizontally
polarized, especially so when the dipole is far from earth.

Best regards, Richard Harrison, KB5WZI