Comparisons are presented between a hybrid Vlasov-Maxwell (HVM
) simulation
of turbulence in a collisionless plasma and fluid reductions. These includ
e Hall-
magnetohydrodynamics (HMHD) and Landau fluid (LF) or FLR-Land
au fluid (FLR-
LF) models that retain pressure anisotropy and low-frequency kin
etic effects such as
Landau damping and, for the last model, finite Larmor radius (FLR) c
orrections.
The problem is considered in two space dimensions, when initial conditio
ns involve
moderate-amplitude perturbations of a homogeneous equilibrium pla
sma subject to
an out-of-plane magnetic field. LF turns out to provide an accurat
e description of
the velocity field up to the ion Larmor radius scale, and even to smaller
scales for
the magnetic field. Compressibility nevertheless appears significant
ly larger at the
sub-ion scales in the fluid models than in the HVM simulation. High freque
ncy ki-
netic effects, such as cyclotron resonances, not retained by fluid
descriptions, could be
at the origin of this discrepancy. A significant temperature anisotr
opy is generated,
with a bias towards the perpendicular component, the more intense
fluctuations being
rather spread out and located in a broad vicinity of current sheets
. Non-gyrotropic
pressure tensor components are measured and their fluctuation
s are shown to reach
a significant fraction of the total pressure fluctuation, with inten
se regions closely
correlated with current sheets.