On the “bowl‐shaped” deformation of planetary equatorial current sheets

Abstract

Arridge et al. (2008) reported evidence for the formation of a “bowl‐shaped” equatorial current disk in Saturn's magnetosphere during epochs with large planetary dipole tilt angle from perpendicularity with the Sun‐planet axis. Using a large multiyear set of Geotail, Polar, and Time History of Events and Macroscale Interactions spacecraft data and a simple model of the magnetic field reversal surface, we found that a similar kind of the tilt‐related magnetic field deformation is present in the Earth's magnetosphere. Based on the properties of a tilted vacuum magnetic field configuration, we conclude that the bowl‐shaped distortion is a universal feature of magnetospheres with a tilted planetary dipole, resulting from the joint effect of the north‐south asymmetry due to the tilt and of the day‐night asymmetry imposed by the solar wind flow.