  The nonlinear evolution of the Kelvin Helmholtz instability in a magnetized
plasma with a perpendicular flow close to, or in, the supermagnetosonic regime
can produce a significant parallel-to-perpendicular pressure anisotropy. This
anisotropy, localized inside the flow shear region, can make the configuration
unstable either to the mirror or to the firehose instability and, in general,
can affect the development of the KHI. The interface between the solar wind and
the Earth's magnetospheric plasma at the magnetospheric equatorial flanks
provides a relevant setting for the development of this complex nonlinear
dynamics.
