  In a recent work Grappin et al. [1] have shown that low- frequency movements
can be transmitted from one footpoint to the other along a magnetic loop, thus
mimicking a friction effect of the corona on the photosphere, and invalidating
the line-tying approximation. We consider here successively the effect of high
frequencies and turbulent damping on the process. We use a very simple
atmospheric model which allows to study analytically the laminar case, and to
study the turbulent case both using simple phenomenological arguments and a
more sophisticated turbulence model [2]. We find that, except when turbulent
damping is such that all turbulence is damped during loop traversal, coupling
still occurs between distant footpoints, and moreover the coronal field induced
by photospheric movements saturates at finite values.
