the problem of the wind – ambient medium interaction is identical to the problem of collision between a wide relativistic beam of cold plasma and a region with a strong magnetic field which is called a magnetic barrier. Recently, the interaction of a wide relativistic plasma beam with a magnetic barrier was studied numerically ([@Smolsky96]; [@Usov98]). In these studies, the following initial condition of the beam – barrier system was assumed. Initially, at $t=0$, the ultrarelativistic homogeneous neutral beam of protons and electrons (number densities $n_p=n_e\equiv n_0$) runs along the $x$ axis and impacts at the barrier, where $n_0$ is constant. The beam is infinite in the $y$ – $z$ dimensions and semi-infinite in the $x$ dimension. The magnetic field of the barrier ${\bf B}_0$ is uniform and transverse to the beam velocity, ${\bf B}_0=B_0{\bf \hat e}_z\Theta[x]$, where $B_0$ is constant and $\Theta [x]$ is the step function equal to unity for $x>0$ and to zero for $x<0$. At the front of the barrier, $x=0$, the surface current $J_y$ runs along the $y$ axis to generate the jump of the magnetic field. The value of this current per unit length of the front across the current direction is $cB_0/4\pi$. A 