\begin{table}%t1
\caption{\label{tab:units}Normalization units.}
%\centering
\par
\begin{tabular}{ccc}
\hline\hline
\noalign{\smallskip}
Quantity & Symbol(s) & Unit \\
\hline
    length          & $x$, $y$, $z$, $r$, $R$   & $l_0$ \\
    gas pressure    & $p$                   & $p_0$ \\
    density         & $\rho$                & $\rho_0$ \\
    velocity        & $v$                   & $\cso = \sqrt{ \gamma p_0 / \rho_0 }$ \\
    time            & $t$                   & $t_0 = l_0 / \cso$ \\
    energy flow rate& $\efrate$             & $p_0 l_0^3 / t_0$ \\
    magnetic flux density       & $B$       & $B_0 = \sqrt{8 \pi p_0} $ \\
\hline
\end{tabular}
\end{table}