What empirical evidence is there for displacement current? I wonder what more or less direct measurements of the displacement current exist.  I know that the existence of em waves demonstrates its existence, though somewhat indirectly.  I also know that there have been sensitive magnetic field measurements between charging parallel plate capacitors, but it has been argued that these can be explained in terms of the conduction currents flowing within the plates (Bartlett, Am. J. Phys. 58 (12), 1168 (1990) ).  Any others?
Update:  I ran across an interesting article showing an alternative to the displacement current to make Maxwell's equations consistent with charge conservation, but it fails to predict em waves (Wolsky, Euro. J. Phys. 36 (2015) 035019).  It's interesting because it underscores that the displacement current is a theoretical construct.  Is there evidence for it that does not invoke Faraday's law?
 A: R. Van Cauwenberghe is regarded as author of the first direct measurement of the displacement current, in 1929, as you can check in this link that will redirect you to the Journal de Physique.    
For a more recent experiment, check this paper from the Physical Review Letters: it also provides a short interesting historical introduction about the attempts to measure the displacement currents. I suggest you not to skip the footnotes!
A: The simplest evidence is the ac current going through a perfectly insulating capacitor with capacitance $C$ $$i= j\omega C v$$ where $i$ and $v$ are the complex current and voltage amplitudes, $j$ is the imaginary unit, and $\omega$ is the angular frequency of the ac voltage and current.
The conduction current in the wires continues as a displacement current $$i_D=Aj\omega \epsilon E$$ in the dielectric of the capacitor. $A$ is the area of the capacitor, $E$ is the electric field ac amplitude, $\epsilon$ is the absolute dielectric permittivity. This displacement current flowing in the dielectric is equal to the current through the capacitor given above.
