The physical processes in the subauroral ionosphere

Phenomena that occur in the subauroral ionosphere are discussed in terms of magnetosphere-ionosphere interactions. The appearance of the electric field in the subauroral ionosphere is examined. It is found that the two main structures of the electric field are caused by penetration of the magnetospheric electric field through the shielding layer at the plasmapause and generation of a new polarization field in the outer plasmasphere by a spatial separation of the ring-current particles. The main mechanisms for the decay of ionization and generation of the midlatitude ionospheric trough and the excitation of stable auroral red arcs in the subauroral ionosphere are examined.