ABSTRACT
This chapter describes processes in the solar wind, foreshock, and magnetosheath that modify incoming solar wind plasma prior to its interaction with the magnetosphere. It begins by identifying which magnetosheath parameters need to be understood to predict the nature of each of the interaction mechanisms. Some of the magnetosheath magnetic field lines that drape against the dayside magnetopause reconnect with magnetospheric magnetic field lines. Magnetosheath and magnetospheric magnetic field lines connect through the apices of the flattened magnetotail via a transition region many Earth radii wide. The solar wind and magnetosheath flow sweeps all of the waves generated in the upstream region across the bow shock and into the magnetosheath. Whatever their origin is, the significance of the mirror mode and mirror mode-like density structures within the magnetosheath lies in their ability to trigger transient, patchy reconnection at the dayside magnetopause. Within magnetohydrodynamic simulations, the transmission of tangential discontinuities across the bow shock might be considered a relatively simple matter.
