Plasma sheet of the magnetosphere of the Earth as the turbulent wake and magnetosphere-ionosphere coupling

The formation of the turbulent wake is a common property of any fluid flow with large Reynolds number in the vicinity of an obstacle. Multiple results of experimental observations demonstrate the same situation in the case of the magnetosphere of the Earth. The main difference is connected with the scales of the turbulent wake. The scale of the turbulent wake in the direction transverse to flow is the same as the scale of the obstacle. The scale of the plasma sheet, which is the region of the turbulent flow in the magnetosphere of the Earth when Bz IMF<0, is the same as the scale of the magnetosphere in Y direction (∼ 40Re) and much smaller in Z direction (∼ 5 Re). The role of the magnetosphere-ionosphere interactions in the formation of such feature of turbulent wake is analyzed. The large-scale dawn-dusk electric field is considered as the zero mode of magnetospheric turbulence. This field compresses the plasma of the plasma sheet producing the asymmetry in Y and Z directions. Dissipation of the energy of the harmonics of the magnetospheric turbulence includes not only ionospheric heating but also the field-aligned and transverse acceleration of electrons and ions, the formation of shell-type and conic-type distribution functions. The acceleration of the ions of the ionospheric origin change the distribution of the magnetospheric plasma pressure. The influence of the process of particle acceleration on structure and amplitudes of magnetospheric turbulence is discussed. The explanation of such feature is connected with the turbulent mode interactions. The magnetosphere-ionosphere interactions is the main feature of the formation of large and medium-scale harmonics of magnetospheric turbulence. Given by Antonova and Ovchinnikov (1998) as (see Antonova and Tverskoy, 1998), acts to compress the plasma sheet and medium-scale modes act to expel it. The equilibrium of the compression and the expansion processes determine the scale of the plasma sheet in Z direction. The weakening of the dawn-dusk electric field under B_z^IMF >0 conditions leads to filling of the tail lobe by plasma from the plasma sheet according to observations of Huang et al. (1989). In such a case the scale of the magnetospheric turbulent wake becomes the same in Y and Z directions.