  Ion anisotropies can affect a host of processes within the magnetosphere,
from modifying the growth rate of various instabilities to the energization and
mass transport within the magnetosphere. Global multi-fluid simulations using a
full treatment of the pressure tensor are used to evaluate the influence of
temperature anisotropies on the magnetospheric dynamics for an idealized
substorm. The simulations are able to resolve the development of conics over
the polar cap which eventually turn into beams in the lobes. Entry of this
plasma, particularly heavy ions with high Tparallel, leads to a faster
reconnection rate, additional turbulence within the reconnection region, and
the substorm onset time occurs approximately 5 min earlier relative to
isotropic simulations. The anisotropic treatment yields much more intense
auroral currents on the nightside associated with onset and a faster expansion
phase of the substorm. The plasma entering into the current sheet experiences
stronger heating in the anisotropic simulations, which increases plasma
transport into the equatorial dayside. Hence, the convection of the
plasmasphere towards the dayside magnetosphere during the growth phase is
accompanied by a relative increase in Tparallel. This leads to a very distinct
temperature profile on the dayside. The injection of the energetic particles
from the substorm leads to an overall increase Tperpendicular on the dayside,
but only O+ reaches sufficient energies for the bulk of these ions to be able
to cross noon local time during the expansion phase to participate in the
formation of symmetric ring current. The net effect from these processes is to
decrease the cross-polar cap potential, modify the timing of the development of
reconnection and the development of the auroral currents and enhance the
injection of energetic particles into the inner magnetosphere.
