  Line-of-sight magnetograms for 217 active regions (ARs) of different flare
rate observed at the solar disk center from January 1997 until December 2006
are utilized to study the turbulence regime and its relationship to the flare
productivity. Data from {\it SOHO}/MDI instrument recorded in the high
resolution mode and data from the BBSO magnetograph were used. The turbulence
regime was probed via magnetic energy spectra and magnetic dissipation spectra.
We found steeper energy spectra for ARs of higher flare productivity. We also
report that both the power index, $\alpha$, of the energy spectrum, $E(k) \sim
k^{-\alpha}$, and the total spectral energy $W=\int E(k)dk$ are comparably
correlated with the flare index, $A$, of an active region. The correlations are
found to be stronger than that found between the flare index and total unsigned
flux. The flare index for an AR can be estimated based on measurements of
$\alpha$ and $W$ as $A=10^b (\alpha W)^c$, with $b=-7.92 \pm 0.58$ and $c=1.85
\pm 0.13$. We found that the regime of the fully-developed turbulence occurs in
decaying ARs and in emerging ARs (at the very early stage of emergence).
Well-developed ARs display under-developed turbulence with strong magnetic
dissipation at all scales.
