  A plasma loop twisted Riemannian model is applied to torus dynamos twisted
flows it leading to a slow dynamo such as in Moebius strip dynamo, recently
considered by Shukurov, Stepanov and Sokoloff [Phys. Rev. \textbf{E
78},025301,(2008)] to modelling Perm dynamo torus in liquid sodium. Since
diffusion and advection (stretching), are competing effects for dynamo action,
plasma resistivity term is shown to be proportional to loops Riemann curvature
(folding). Shukurov et al, also showed that based on Ponomarenko dynamo, a
broader torus channel produces a better dynamo. These results agree with
Schekochihin et al [Phys Rev \textbf{E} (2002)] where random filamentary
magnetic fields are strengthen by curvature. Analysis of spectrum of chaotic
fast dynamos, shows that Riemann curvature acts as a damping, since growth
magnetic field rate is inversely proportional to Riemann curvature. Comparison
with general relativistic MHD dynamo equation, shows that the Ricci tensor,
which is a contraction of the Riemann tensor also appears in the diffusion
term. Curvature of plasma loop is
${{R^{1}}_{212}}|_{\textbf{Plasma}}\approx{5.6{\times}10^{-19}m^{-2}}$, while
for Perm torus is certainly higher. Thus slow dynamos are favoured in dynamo
laboratories rather than in plasma loops. It is shown that the
curvature-stretching flux rope dynamo coupling energy, coincides with the
minimum twist energy ${\epsilon}_{\textbf{twist}}\approx{10^{30}TeV}$ stored in
flux ropes. Torus flux tubes around black-holes remain in the order of $2MeV$
and GBR are around $10^{52}TeV$. Since the ${R^{1}}_{212}$ is negative,
inflexionary flux tubes fast dynamos may be responsible for this CME mechanism
in UHF plasma loops.
