Interaction of Solar Wind with Earth's Magnetosphere and Formation of Magnetospheric Boundary Layers

Popular picture of the interaction of the solar wind with the magnetosphere of the Earth considers the reconnection process as the dominant process leading to the plasma penetration inside the magnetosphere. Such explanations do not include the analysis of magnetopause stress balance. However, local destruction of such balance can be the source of magnetosheath plasma penetration inside the magnetosphere. Solar wind is the turbulent medium. Plasma density and velocity, interplanetary magnetic field constantly fluctuate. Such fluctuations are greatly increased near the magnetosphere in the magnetosheath region. The role of fluctuations of magnetic field in the magnetosheath in the formation of magnetospheric boundary layers is studied using data of high apogee satellites of THEMIS project. The fluctuations of magnetic field differ from point to point in the magnetosheath. Magnetic field fluctuations in the magnetosheath do not produce real contribution to the stress balance on the magnetopause in the subsolar point as the amplitudes of such fluctuations are much smaller than the magnetospheric magnetic field in the subsolar point. Minimal values of the magnetic field on the dayside magnetic field lines take place far from the equatorial plane. Magnetic field in such minima is much smaller than the magnetic field at the equator. This means that magnetosheath plasma can penetrate inside the magnetosphere and form the magnetospheric boundary layers in the near cusp region, where the fluctuations of the plasma parameters and the magnetic field are higher than in the subsolar point and the amplitudes of magnetic field fluctuations exceed the values of magnetic field inside the magnetosphere.