\begin{table}%t1
\caption{\label{tab1}Proton and electron gyro-periods and gyro-radii.}
%%\centering

\par
\begin{tabular}{ c  c  c  c  c} 
\hline\hline \noalign{\smallskip}                           
 & \multicolumn{2}{c}{$B=10^{-3}$~T}
 & \multicolumn{2}{c}{$B=10^{-2}$~T}\\
 & p$^{+}$ & e$^{-}$ & p$^{+}$ & e$^{-}$\\
\hline 
\multicolumn{5}{c}{Gyro-radii $R_{\rm g}$, m}\\
$\mathcal{E}$, keV & \multicolumn{4}{c}{}\\
$10^{-1}$ &$1.4$ &$3.4\times 10^{-2}$ &$1.4\times 10^{-1}$  &$3.4\times 10^{-3}$ \\
$10^{ 1}$ &$1.4\times 10^1$ &$3.4\times 10^{-1}$ &$1.4$ &$3.4\times 10^{-2}$ \\
$10^{ 3}$ &$1.4\times 10^2$ &$3.4$ &$1.4\times 10^1$  &$3.4\times 10^{-1}$ \\
\hline
\multicolumn{5}{c}{Gyro-periods $\mathcal{T}$, s}\\
&$6.6\times 10^{-5}$ &$3.6\times 10^{-8}$ &$6.6\times 10^{-6}$ &$3.6\times 10^{-9}$ \\
\hline
\end{tabular}
\end{table}