\begin{table}%t2 [htbp]
  %%\centering

\par
  \caption{\label{tab:Vitesse}Parameters for the three rotation profiles used
    to mimic the azimuthal velocity of the plasma 
    in the electrospheric disk.}
  \begin{tabular}{cccc}
    \hline\hline
    $\Omega$ & $\alpha$ & $\beta$ & $r_0$ \\
    \hline\noalign{\smallskip}
    $\Omega_1$ & 3.0 & $5\times10^{-5}$ & 6.0 \\
    $\Omega_2$ & 1.0 & $5\times10^{-5}$ & 6.0 \\
    $\Omega_3$ & 0.3 & $5\times10^{-5}$ & 10.0 \\
    \hline
  \end{tabular}
\end{table}