  The Brownian motion of a charged test particle caused by quantum
electromagnetic vacuum fluctuations between two perfectly conducting plates is
examined and the mean squared fluctuations in the velocity and position of the
test particle are calculated. Our results show that the Brownian motion in the
direction normal to the plates is reinforced in comparison to that in the
single-plate case. The effective temperature associated with this normal
Brownian motion could be three times as large as that in the single-plate case.
However, the negative dispersions for the velocity and position in the
longitudinal directions, which could be interpreted as reducing the quantum
uncertainties of the particle, acquire positive corrections due to the presence
of the second plate, and are thus weakened.
