  The relationship between a decaying strong turbulence and the mirror
instability in a slowly expanding plasma is investigated using two-dimensional
hybrid expanding box simulations. We impose an initial ambient magnetic field
perpendicular to the simulation box, and we start with a spectrum of
large-scale, linearly-polarized, random-phase Alfvenic fluctuations which have
energy equipartition between kinetic and magnetic fluctuations and vanishing
correlation between the two fields. A turbulent cascade rapidly develops,
magnetic field fluctuations exhibit a Kolmogorov-like power-law spectrum at
large scales and a steeper spectrum at sub-ion scales. The imposed expansion
(taking a strictly transverse ambient magnetic field) leads to generation of an
important perpendicular proton temperature anisotropy that eventually drives
the mirror instability. This instability generates large-amplitude,
nonpropagating, compressible, pressure-balanced magnetic structures in a form
of magnetic enhancements/humps that reduce the perpendicular temperature
anisotropy.
