  New H-alpha Fabry-Perot interferometer observations of the Virgo cluster
spiral galaxy NGC 4522 are presented. A velocity field up to a radius of 60''
was obtained. The observed rotation curve is symmetric. It is not perturbed in
the inner disk. For radii >50'' it shows a solid body rotation. We compare
these data with a numerical model which includes the effects of ram pressure
stripping. The model can reproduce the main characteristics of the H-alpha
emission distribution and velocity field. We therefore conclude that the
stripping event which caused the HI deficiency and the distorted H-alpha
distribution and velocity field has been due to ram pressure. The closest
passage of the galaxy to the cluster center is estimated to be approx. 6.5 10^8
yr ago. The observed recent star formation is due to the re-accretion of gas
clouds which were accelerated to velocities below the escape velocity during
the stripping event. Furthermore, the gas which is located at radii >60'' is
part of an asymmetric expanding ring of gas clouds. A substantial part of these
clouds is located above the disk plane. We predict the HI gas distribution and
velocity field as it would be observed by deep 21 cm observations.
