Results from a numerical study of localized, large-amplitude electromagnetic disturbances measured by the Polar satellite in the nightside plasma sheet are presented. It is shown that these disturbances can be explained in terms of shear Alfvén waves generated in the magnetotail and interacting with a microturbulent layer at low altitudes. The plasma microturbulence/anomalous resistivity self-consistently included in the nonlinear, two-fluid MHD model causes the wave reflection and defines its structure and amplitude in the lower magnetosphere. It also causes the dissipation of the wave energy inside the turbulent/resistive layer, which leads to the creation of parallel electric field and parallel electron acceleration. Thus plasma turbulence connects electromagnetic structures measured by Polar at radial distance 4-6 RE with bright aurora simultaneously observed by the Polar Ultraviolet Imager at the ionospheric footprint of the corresponding magnetic field lines.
- Alfven wave
- Anomalous resistivity
- Auroral phenomena
- Current-driven instabilities
- Magnetosphere-ionosphere coupling