  Recently, detailed real space imaging using scanning tunneling spectroscopy
of the vortex lattice in a weakly pinned a-MoGe thin film revealed that the
vortex lattice melts in two steps with temperature or magnetic field, going
first from a vortex solid to a hexatic vortex fluid and then from a hexatic
vortex fluid to an isotropic vortex liquid. In this paper, we show that the
resistance in the vortex fluid states is extremely sensitive to radio-frequency
electromagnetic perturbation. In the presence of very low-amplitude excitation
above few kilohertz, the resistance increases by several orders of magnitude.
On the other hand when the superconductor is well shielded from external
electromagnetic radiation, the dissipation in the sample is very small and the
resistance is below our detection limit.
