Thickness of the low-latitude boundary layer at different levels of magnetic field fluctuations in the magnetosheath

Abstract

The role of a high fluctuations level in the Earth’s magnetosheath in plasma penetration into the magnetosphere and in the formation of the low-latitude boundary layer (LLBL) has been considered based on the events that occurred on November 1 and 5, 2007, using the THEMIS-A satellite observations. During the selected LLBL crossings the satellite was measuring behind the quasi-parallel and quasi-perpendicular bow shocks. The angle between the magnetic field direction in the solar wind and the normal to the bow shock (ΘBn) has been taken as a parameter reflecting the level of magnetic field and plasma paremeters fluctuations in the magnetosheath. It has been indicated that a thick LLBL is observed when angle ΘBn is small and the turbulence level in the magnetosheath is high. When angle ΘBn is large, the layer thickness decreases. The possible mechanisms by which a thick LLBL is formed are discussed.