EFFECT OF ANOMALOUS CROSS-FIELD DIFFUSION ON THE FIELD-ALIGNED CURRENT GENERATION

First, on the basis of the satellite observations of the broadband ele ctrostatic noise and the Alfven wave noise in the auroral magnetospher e, within a frame of the quasi-linear theory we show that the proton ( anomalous cross-field) diffusion coefficient averaged over the Aux tub e is likely to reach a significant fraction of the Bohm rate at least in the disturbed periods. Second, as an extension of recently proposed model that a pair of the region 1 and region 2 field-aligned currents (FACs) can be generated as a result of ''natural distortion'' of the hot plasma torus (HPT) in the magnetosphere under the influence of the usually prevailing convection with twin vortex cells (when the interp lanetary magnetic field (IMF) is southward), we study the possible eff ect of the anomalous cross-field diffusion on the large-scale FACs res ulting from the HPT polarization. In the magnetosphere, the hot (great er than or similar to 1 keV) plasma particles are primarily distribute d in a magnetic shell which is connected to two ovals of diffuse auror as on the northern and southern polar ionospheres. Such hot plasma pop ulation is called the hot plasma torus (HPT). The numerical calculatio ns specifically show that primary modification of the FAC pattern by t his effect is the appearance of the triple FAC structure (i.e., Upward FAC zone sandwiched between two downward FAC zones) in the midnight s ector, which can be identified from the satellite observations at leas t during substorm periods. As a direct consequence of formation of suc h a triple FAC structure, the Harang discontinuity appears in the elec tric potential pattern. Thus the formation of the Harang discontinuity can be understood as a result of the HPT polarization by both effects of magnetic drift and anomalous cross-field diffusion.