  We revisit the electromagnetic heat transfer between a metallic nanoparticle
and a metallic semi-infinite substrate, commonly studied using the electric
dipole approximation. For infrared and microwave frequencies, we find that the
magnetic polarizability of the particle is larger than the electric one. We
also find that the local density of states in the near field is dominated by
the magnetic contribution. As a consequence, the power absorbed by the particle
in the near field is due to dissipation by fluctuating eddy currents. These
results show that a number of near-field effects involving metallic particles
should be affected by the fluctuating magnetic fields.
