IGPP Seminar Series

Simulations and Observations of Kelvin-Helmholtz Waves at Saturn's Magnetopause

by Raymond J. Walker


Saturn is like Jupiter in is a rapid rotator. In global simulations vortices form along Saturnís dawn side magnetopause when there is high velocity shear and the condition for the generation of Kelvin Helmholtz (K-H) waves is met. The waves occur when kd~1 where k is the wave number and d is the thickness of the magnetopause boundary layer. K-H waves form on both the magnetopause and the inner edge of the boundary layer. The waves are similar to those found in simulations of the Earthís magnetosphere. The main difference is that at Saturn rotating flows are important for making the boundary unstable. The waves form for northward interplanetary magnetic field (IMF) and not for southward IMF. For northward IMF the effect of reconnection is to enhance the electric field on the dawn side so that rotating flows within the magnetosphere are enhanced. This leads to instability. About 20h after a northward IMF interacts with the dayside magnetopause reconnection occurs in the tail. Flows from the tail to the dayside reduce the plasma density in the dayside magnetosphere causing the boundary to become stable. Within the magnetosphere the K-H waves lead to oscillations in the magnetic field. Similar oscillations are found in Cassini observations.
Tuesday, 09 March 2010
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM