Flash, 14 MByte
The animation shows the total plasma density during eight minutes real time. A logarithmic color scales is used. The black line is the MESSENGER trajectory. The density within the boundary layer (yellow) is significantly larger than the inner magnetosphereic density (green), thereby causing the dayside diamagnetic decrease.
The animation on the right side illustrates the macroscopic density of solar wind ions that enter Mercury's magnetosphere at its dawn side flank. Subsequently they are accelerated planetward and trapped on closed planetary field lines. The ions populate the dayside boundary layer while bouncing from pole to pole (green arc).
The animation on the left-hand side again shows solar wind ions that enter Mercury's magnetosphere but from a different view. The ions that populate the boundary layer stay off Mercury's surface at an equatorial altidude that equals the position of the dayside boundary layer's inner edge. The related density and pressure gradients form a diamagnetic current system.