The distribution of vorticity in auroral arcs

The role of U or V shaped potential structures in the formation of auroral arcs is discussed, with attention given to the links and effects of vortices and the arcs. Individual curl systems have been observed in active auroral arcs, and move with the fluid elements. The vortices are governed by the dispersion relation for the Kelvin-Helmholtz instability and can be mapped in the ionosphere, while the perpendicular electric field cannot. The U and V shaped potential structure is characterized analytically by the electrostatic potential as a means to model the height of a 'referred electric field', which exists as a product of the presence of an equipotential magnetic field in the ionosphere. Observations by the S3-3 satellite have shown that predictions of a model auroral curl system having a horizontal thickness of 10 km and a charge distribution with height are accurate in both magnitude and direction