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Ion anisotropies can affect a host of processes within the magnetosphere,from modifying the growth rate of various instabilities to the energization andmass transport within the magnetosphere. Global multi-fluid simulations using afull treatment of the pressure tensor are used to evaluate the influence oftemperature anisotropies on the magnetospheric dynamics for an idealizedsubstorm. The simulations are able to resolve the development of conics overthe polar cap which eventually turn into beams in the lobes. Entry of thisplasma, particularly heavy ions with high Tparallel, leads to a fasterreconnection rate, additional turbulence within the reconnection region, andthe substorm onset time occurs approximately 5 min earlier relative toisotropic simulations. The anisotropic treatment yields much more intenseauroral currents on the nightside associated with onset and a faster expansionphase of the substorm. The plasma entering into the current sheet experiencesstronger heating in the anisotropic simulations, which increases plasmatransport into the equatorial dayside. Hence, the convection of theplasmasphere towards the dayside magnetosphere during the growth phase isaccompanied by a relative increase in Tparallel. This leads to a very distincttemperature profile on the dayside. The injection of the energetic particlesfrom 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 ableto cross noon local time during the expansion phase to participate in theformation of symmetric ring current. The net effect from these processes is todecrease the cross-polar cap potential, modify the timing of the development ofreconnection and the development of the auroral currents and enhance theinjection of energetic particles into the inner magnetosphere.

The Influence of Temperature Anisotropies in Controlling the Development of Magnetospheric Substorms