  We present results of 3-D numerical simulations of a fast magnetic twister
excited above a foot-point of the potential solar coronal arcade that is
embedded in the solar atmosphere with the initial VAL-IIIC temperature profile,
which is smoothly extended into the solar corona. With the use of the FLASH
code, we solve 3-D ideal magnetohydrodynamic equations by specifying a twist in
the azimuthal component of magnetic field in the solar chromosphere. The
imposed perturbation generates torsional Alfv\'en waves as well as plasma
swirls that reach the other foot-point of the arcade and partially reflect back
from the transition region. The two vortex channels are evident in the
generated twisted flux-tube with a fragmentation near its apex that results
from the initial twist as well as from the morphology of the tube. The
numerical results are compared to observational data of plasma motions in a
solar prominence. The comparison shows that the numerical results and the data
qualitatively agree even though the observed plasma motions occur over
comparatively large spatio-temporal scales in the prominence.
