Illia Silin, University of Alberta, Edmonton, Canada
 
Anomalous resistivity due to lower-hybrid drift waves. Results of Vlasov-code 
simulations and Cluster observations at the magnetopause.
 
 
ABSTRACT. Anomalous resistivity allows incorporation of small-scale kinetic
processes in the large-scale fluid or magnetohydrodynamic phenomena. The
problem of anomalous collisionality and resistivity in collisionless plasmas
due to waves is examined using a general perturbation approach. The role of
lower-hybrid drift (LHD) waves in producing anomalous collisionality in the
vicinity of thin current sheets is considered. LHD waves are quite common in
the Earth magnetosphere, they exist in the regions of plasma density and
magnetic field gradients. Previous attempts to estimate the anomalous
collision rate due to LHD waves, based on quasi-linear estimates and linear
dispersion relation, predicted a very small contribution of the
electrostatic fluctuations, while the electromagnetic fluctuations were
neglected completely. We carried out self-consistent Vlasov-code simulations
of thin current sheets and analyzed plasma and electromagnetic fields
fluctuations measured by Cluster spacecraft during a magnetopause crossing.
Our results suggest that, when the LHD waves reach a highly non-linear
phase, the electrostatic and electromagnetic fluctuations contribute
approximately equally to anomalous collision rate, which is of the order of
lower-hybrid frequency. Anomalous resistivity based on such collision rate
is much higher than predicted by quasi-linear theory and is significant for
large-scale dynamics of the magnetosphere.