Spatial Profile of the LLBL: Multispacecraft Themis observations

Low-latitude boundary layer (LLBL) can be considered as an interface between magnetosheath and plasma sheet and it mediates the transfer of plasma between these regions. Its spatial profile thus can bring important information on the processes involved. The paper presents a case study of five-point LLBL observations. We have used simultaneous observations of five Themis spacecraft and found smooth and monotonous changes of the ion density and temperature over a distance of about 1 R(E) under quiet upstream conditions and northward pointing magnetosheath magnetic field. We propose that the observations suggesting a non-monotonous profile of the parameters during disturbed conditions would be interpreted in terms of distorted magnetopause surface and that the monotonous profiles are kept even under such conditions.