  The magnetopause boundary implies two kinds of variations: a density/
temperature gradient and a magnetic field rotation. These two kinds are always
observed in a close vicinity of each other, if not inseparably mixed. We
present a case study from the Cluster data where the two are clearly separated
and investigate the natures of both layers. We evidence that the first one is a
slow shock while the second is a rotational discontinuity. The interaction
between these two kinds of discontinuities is then studied with the help of
1,5-D magnetohydrodynamics simulations. The comparison with the data is quite
positive and leads to think that most of the generic properties of the
magnetopause may be interpreted in this sense.
