"The current which flows on the outer surface of the shield is called common
mode current. In other words, it is the unbalanced current not returned
within the coaxial cable.
This leads to a very important question. If the current isn't returned in
the cable, where does it go? The answer is, it radiates! In fact, the amount
of radiation from the coax cable is directly proportional to the common-mode
current on that cable." From: http://www.k0bg.com/common.html

"In fact, the amount of radiation from the coax cable is directly
proportional to the common-mode current on that cable."

The currents consists of electrons.

Does it means that the electrons jump off from the end of the radiator?

In Faraday time no such meters but Faraday had know that electrons (nuclei)
jump off from the end of the open circuit.

Also L. Lorenz known that the light is the oscillatory flow of electrons.

S*