Analysis of temperature versus density plots and their relation to the LLBL formation under southward and northward IMF orientations

摘要

The paper reports a clear dependence of a basic structure of two sublayers of the low-latitude boundary layer (LLBL) on northward and southward interplanetary magnetic field (IMF) orientations. Regardless of different processes responsible for a formation and evolution of the entire LLBL, the outer part of the LLBL is significantly influenced by the sign of the IMF B_Z component. Under northward IMF conditions this layer is present, whereas it is missing during a southward pointing IMF. This behavior can be understood in terms of a motion of reconnection spots due to the changes of the orientation of the magnetosheath magnetic field in the vicinity of the magnetopause. Our case and statistical studies demonstrate that the changes of the LLBL structure can be observed in the subsolar region as well as on flanks near the dawn-dusk meridian. Moreover, the study emphasizes a role of magnetosheath magnetic field variations on the boundary layer formation.