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Geophysical Research Letters

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

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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.

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