What is displacement current? Antenna and electromagnetic books talk of
displacement current flowing in an insulator or dielectric and providing a
magnetic field like a real current. They make out that the magnetic field is
distributed the same way as if a real current was flowing along a
conductor. Displacement current is called a virtual current. Books refer to
a real current flowing in a conductor, and being converted to a displacement
current where the conductor stops. Wikepedia says that displacement current
is proportional to the time derivative of the changing electric field, where
a changing electric field induces a changing magnetic field. Diagrams show
displacement currents flowing through the air in the near field of the
antenna. Some scientists believe that displacement current is formed by
virtual photons. It appears that virtual photons are hard to investigate in
particle accelerators.

Displacement current is usually introduced as the virtual current that flows
through the dielectric of a capacitor. Does such a current really exist?