IMF Bz as Dominant Factor for the LLBL Formation

The low-latitude boundary layer (LLBL) is defined as a region where the magnetosheath plasma population was found on the magnetospheric side of the magnetopause current layer at low latitudes. In spite of its crucial role in the solar wind - magnetosphere coupling, basic LLBL parameters and their relations to upstream conditions are still under debate. IMF Bz seems to be the significant factor for the formation of interface layer that the LLBL is. To discuss the changes of the inner and outer LLBL sublayers, their presence and thickness at the dayside magnetopause in different local times under various upstream conditions as well as modification of their spatial profiles the data from five THEMIS spacecraft were used. We present the analysis of the reformation process of the LLBL in response to changes of the IMF direction from northward to southward or vice versa. It stresses out the importance of the magnetosheath fluctuations for the boundary layer formation.