The IMF bending upstream of the Martian bow shock

Abstract

A noticeable bending of the magnetic field lines in the Martian upstream region is observed. Variations of the field are controlled by the IMF and the foreshock geometry. The sign of ΔB changes at the crossing of the tangent surface, which borders foreshock and the undisturbed solar wind. Perturbations of the magnetic field are centered at the plane which is normal to the tangent surface and intersects the bow shock at the tangent point. All observed signatures suggest that the current, providing field variations, is localized near the tangent surface. Although, two models are discussed, neither of them is able to explain all observed features satisfactorily.