  Exclusive coherent and incoherent electroproduction of the $\rho^0$ meson
from $^1$H and $^{14}$N targets has been studied at the HERMES experiment as a
function of coherence length ($l_c$), corresponding to the lifetime of hadronic
fluctuations of the virtual photon, and squared four-momentum of the virtual
photon ($-Q^2$). The ratio of $^{14}$N to $^1$H cross sections per nucleon,
known as nuclear transparency, was found to increase (decrease) with increasing
coherence length for coherent (incoherent) $\rho^0$ electroproduction. For
fixed coherence length, a rise of nuclear transparency with $Q^2$ is observed
for both coherent and incoherent $\rho^0$ production, which is in agreement
with theoretical calculations of color transparency.
