Bifurcated current sheet: model and Cluster observations

Cluster observations have recently confirmed previous ISEE and Geotail observations showing that the magnetotail current sheet can present a bifurcated structure with two off-centre current peaks. We show in this paper that such a structure can be described by a kinetic tangential equilibrium which is an exact solution of the Vlasov-Maxwell equations. A tangential equilibrium is characterized by a bulk plasma velocity and magnetic field perpendicular to the density and/or temperature gradient direction. The particle distribution functions are sums of an infinite number of elementary functions parametrized by a vector potential. The model is consistent with Cluster observations of a plasma density plateau between the current peaks and the typical size and amplitude of the current distribution. We briefly review existing models and propose some studies which could be carried out with our model.