  It was recently found that thermodynamic anomalies which arise in the Casimir
effect between metals described by the Drude model can be attributed to the
interaction of fluctuating Foucault (or eddy) currents [Phys. Rev. Lett. 103,
130405 (2009)]. We show explicitly that the two leading terms of the
low-temperature correction to the Casimir free energy of interaction between
two plates, are identical to those pertaining to the Foucault current
interaction alone, up to a correction which is very small for good metals.
Moreover, a mode density along real frequencies is introduced, showing that the
Casimir free energy, as given by the Lifshitz theory, separates in a natural
manner in contributions from eddy currents and propagating cavity modes,
respectively. The latter have long been known to be of little importance to the
low-temperature Casimir anomalies. This convincingly demonstrates that eddy
current modes are responsible for the large temperature correction to the
Casimir effect between Drude metals, predicted by the Lifshitz theory, but not
observed in experiments.
