Magnetospheric current sheets

A review is presented of theories and observations of current sheets in the magnetosphere, emphasizing the magnetopause and tail current sheets. Theoretical models of the magnetopause current sheet can be divided into two types: specular reflection and fluid models containing no external magnetic field, and models with an interplanetary/magnetosheath magnetic field. Our understanding of the first type is much better than of the second, although magnetospheric observations indicate that the external magnetic field plays an important role. Most of the theoretical models of the tail current sheet attempt to arrive at an understanding of the reconnection process or start with the assumption that reconnection is important. Observations are reviewed and implications for the models are discussed.