  Galactic dynamo models take as input certain parameters of the interstellar
turbulence, most essentially the correlation time $\tau$, root-mean-square
turbulent speed $u$, and correlation scale $l$. However, these quantities are
difficult, or, in the case of $\tau$, impossible, to directly observe, and
theorists have mostly relied on order of magnitude estimates. Here we present
an analytic model to derive these quantities in terms of a small set of more
accessible parameters. In our model, turbulence is assumed to be driven
concurrently by isolated supernovae (SNe) and superbubbles (SBs), but
clustering of SNe to form SBs can be turned off if desired, which reduces the
number of model parameters by about half. In general, we find that isolated SNe
and SBs can inject comparable amounts of turbulent energy into the interstellar
medium, but SBs do so less efficiently. This results in rather low overall
conversion rates of SN energy into turbulent energy of $\sim1$-$3\%$. The
results obtained for $l$, $u$ and $\tau$ for model parameter values
representative of the Solar neighbourhood are consistent with those determined
from direct numerical simulations. Our analytic model can be combined with
existing dynamo models to predict more directly the magnetic field properties
for nearby galaxies or for statistical populations of galaxies in cosmological
models.
