In this Communication, we consider a simple model of magnetosphere around a fast rotating Jupiter–like object possessing a spin–aligned dipolar moment μ. In this model, low–energy plasma released by inner sources located beyond the corotation radius diffuses outward through closed lines, forming a thin equatorial disk in which there is a quasistatic balance between the centrifugal force and the magnetic tension. At some critical radius r0, however, the magnetic field is no longer strong enough to hold the matter, and blows open, the matter escaping freely (Fig. 1) (this model has been introduced by Hill and Carbary, 1978).