  We study analytically the relaxation dynamics of charged test fields left
outside a newly born charged black hole. In particular, we obtain a simple
analytic expression for the fundamental quasinormal resonances of near-extremal
Reissner-Nordstr\"om black holes. The formula is expressed in terms of the
black-hole physical parameters: $\omega=q\Phi-i2\pi T_{BH}(n+{1 \over 2})$,
where $T_{BH}$ and $\Phi$ are the temperature and electric potential of the
black hole, and $q$ is the charge of the field.
