• comet tails;
  • discontinuities;
  • magnetotail disconnection;
  • velocity shear;
  • vorticity

[1] The solar wind is filled with strong current sheets and sudden velocity shears; often the two are co-located. Sudden velocity shears at 1 AU are statistically analyzed using ACE measurements from 1998 to 2008. The occurrence rates of passage and the orientations of the shear planes are examined. For shear layers with vector velocity changes |Δv| > 50 km/s, an average of ∼12 pass the Earth per day. In the fast wind, ∼60 sudden shear layers pass the Earth per day (about 2.5 per hour). To explore the effects of sudden wind shears on the Earth's magnetosphere, global magnetospheric MHD simulations with four different simulation codes are performed at the Community Coordinated Modeling Center (CCMC) with north-south and east-west wind shears. Windsock movement of the magnetotail is analyzed and comet-like disconnections of the magnetotail and magnetosheath are examined. Sudden changes in the cross-polar-cap potential and ionospheric Joule dissipation are seen as the shear layers pass the Earth. Other potential effects of sudden wind shear on the magnetosphere are discussed.